CHPM2030 Deliverable D1 -...

Report on data availabilityCHPM2030 Deliverable D1.2Version: December 2016

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 654100.

Author contactGerhard SchwarzGeological Survey of SwedenBox 670 751 28 Uppsala SwedenEmail: [email protected]

Published by the CHPM2030 project, 2016University of MiskolcH-3515 Miskolc-EgyetemvárosHungaryEmail: [email protected]

CHPM2030 DELIVERABLE D 1.2

REPORT ON DATA AVAILABILITY

Summary:

This report aims to provide a brief overview of four major ore districts in Europe, namely in SW

England, southern Portugal, NW Romania and central and northern Sweden. It is completed with a

survey of existing boreholes in the European countries, where temperatures at depth in access of

100oC are observed. The report includes descriptions of the geological settings, and on-going efforts in

geophysics in seeing deeper and increasing resolution for detecting mineralized zones at depth, as

well as attempting to estimate their geothermal potential.

Authors:

Gerhard Schwarz, geophysicist, Magnus Ripa, geologist, Bo Thunholm, hydrogeologist (Geological

Survey of Sweden)

Richard A Shaw, economic geologist, Keith Bateman, geochemist, Eimear Deady, economic geologist,

Paul Lusty, economic geologist (British Geological Survey)

Elsa Cristina Ramalho, geological engineer, João Xavier Matos, economic geologist, João Gameira

Carvalho, geophysicist (Laboratório Nacional de Energia e Geologia)

Diana Perșa, researcher, Ștefan Marincea, senior researcher, Albert Baltreș, senior researcher,

Constantin Costea, senior researcher, Delia Dumitraș, senior researcher, Gabriel Preda, GIS editor

Vanja Bisevac, geologist, Isabel Fernandez, geologist (European Federation of Geologists, Geologist)

This project has received funding from the European Union’s Horizon 2020 research and

innovation programme under grant agreement nº 654100.

CHPM2030 DELIVERABLE 1.2

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Table of contents Extended summary ....................................................................................................................... 4

0 Preface ................................................................................................................................. 5

1 Introduction and outline of work............................................................................................. 6

1.1 Country specific issues .................................................................................................... 6

1.2 Goals ............................................................................................................................. 6

2 Previous research and available data ....................................................................................... 7

2.1 Geology and geophysics, including drilling ........................................................................ 8

2.2 Geometry and composition of ore deposits ...................................................................... 8

2.3 Structural evolution, deep-seated faults and fracture zones, their alignment ...................... 9

2.4 Hydraulic properties, deep fluid flow ............................................................................... 9

2.5 Fluid composition, brines, meteoric waters .................................................................... 12

2.6 Thermal properties and heat flow.................................................................................. 14

2.7 Current metallogenic models (2D- and 3D-) .................................................................... 15

3 Identifying target sites for future CHPM................................................................................. 16

3.1 Extending existing models to greater depth, integrating data down to 7 km ..................... 16

3.2 Knowledge gaps and limitations..................................................................................... 16

4 Discussion and concluding remarks ....................................................................................... 18

Acknowledgements ..................................................................................................................... 18

References ................................................................................................................................. 18

Other sources / Web links ............................................................................................................ 18


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List of Figures

Figure 1. Major ore deposits of Europe (after Weihed 2015), with the mining areas and their available

data described in tasks 1.2.1 to 1.2.4 indicated (see appendices 1.2.1 to 1.2.4), i.e., in the Southwest of

England, Southern Portugal, Northwestern Romania and Central and Northern Sweden .................... 7

Figure 2. Main ore deposits of Europe, with their major ore content and size (class A, B, C) indicated,

according to the ProMine database (after Cassard et al. 2015). ........................................................ 9

Figure 3. Temperature distribution at 1000 m depth in Europe (Schellschmidt and Hurter 2002) ...... 13

Figure 4. Generalised heat flow density map of Europe, based on the Atlas of Geothermal Resources in

Europe (after Hurter and Haenel 2002) ......................................................................................... 14

List of Tables

Table 1. Summarizing data about some of the ore districts of Europe that are the base for the present

report......................................................................................................................................... 10

Table 2. Summary of boreholes drilled in some of the European countries where temperature is above

100oC and mineralisations were identified (see even Appendix D1.5). ............................................. 11

List of Appendices: Availability of Data

A1.2.1: Report on data availability: South West England

A1.2.2: Report on data availability: Portugal, Iberian Pyrite Belt

A1.2.3: Report on data availability: Romania

A1.2.4: Report on data availability: Sweden

A1.2.5: Report on data availability of drill holes: Europe integrated


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Extended summary

This report is a condensed compilation and evaluation of five reports on available data for the

development of orebody enhanced geothermal systems, i.e., the CHPM technology at upper crustal

depths in suitable ore districts of Europe. It will serve as a basis for research on a new type of facility

for Combined Heat, Power and Metal extraction (CHPM). The five reports, written by individual

working groups from the United Kingdom (UK), Portugal, Romania, Sweden and the European

Federation of Geologists (EFG) are attached here in original form as appendices 1.2.1 to 1.2.5. They

mainly comprise geological, geophysical and geochemical data on and descriptions of mineralized

areas in these countries. The EFG report presents a European inventory of drill holes with

temperatures in excess of 100°C, availability of data for these holes, and any metal enrichments

having been encountered at depth.

The target areas in the specified countries belong to three large metallogenic provinces in Europe: the

Precambrian Fennoscandian Shield province, as for Sweden; the late Paleozoic Variscan province, as

for SW England and southern Portugal; and the Mesozoic-Cenozoic Alpine province, as for NW

Romania. In these provinces prospective zones suitable for the CHPM technology should be evaluated.

Much is already known about the geology, mineralisation, fluids and the geothermal potential of the

ore districts, discussed in this report. However, the knowledge often is restricted to the upper 1 000 m

of the crust or less. Locally, where deep drilling has been performed, the conditions may be evaluated

to greater depths. The availability of data has significant implications regarding the accuracy of

modelled conditions in an enhanced geothermal system (EGS) at greater depths. Therefore, the

structural information and the knowledge of the physical state of the upper crust need to be enlarged

considerably in order to meet the goals of the CHPM project.


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0 Preface

This report describes what is already known about the geology, mineralisation, fluids and the

geothermal potential of the areas of interest. It is one of the first deliverables of the CHPM2030

project - an EC-funded Horizon2020 project which aims to develop a novel and potentially disruptive

technology that can help satisfy European needs for energy and critical metals in a single interlinked

process. Working at the frontiers of geothermal resources development, minerals extraction and

electro-metallurgy, the project aims to convert ultra-deep metallic mineralisations into orebody-

enhanced geothermal systems (EGS). It will serve as a basis for the development of a new type of

facility for Combined Heat, Power and Metal extraction (CHPM).

The project will help providing new impetus to geothermal development in Europe by investigating

previously unexplored pathways at low-TRL. This will be achieved by developing a roadmap in support

of the pilot implementation of such system before 2025, and the full-scale commercial

implementation before 2030. It will include detailed specifications of this new type of future EGS

facility (CHPM).

In the technology envisioned, the metal-bearing geological formation will be manipulated in a way

that the co-production of thermal energy and metals will be possible. Four geographical areas have

been chosen for assessment based on pre-existing data and potential for CHPM development in

mineralised areas in the United Kingdom (UK), Portugal, Romania and Sweden. This report summarises

information relevant especially to these four countries, but even for other European regions.

The CHPM project aims to provide proof-of-concept for the following hypotheses:

1. The composition and structure of orebodies have certain favourable characteristics that could be

used to our advantage when developing an EGS.

2. Metals can be leached from orebodies in high concentrations over a prolonged period of time and

may substantially influence the economics of EGS.

3. The continuous leaching of metals will increase system’s performance over time in a controlled

way and without the need to use high-pressure reservoir stimulation, minimising the potential

detrimental impacts of both heat and metal extraction.


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1 Introduction and outline of work

This report is a condensed compilation and evaluation of five reports on the availability of data of

some of the European ore districts for the development of enhanced geothermal systems. These

reports were written by individual working groups from the UK, Portugal, Romania, Sweden and the

European Federation of Geologists (EFG) and are attached here as appendices 1.2.1 to 1.2.5. Their

basic structure was initially agreed upon by the different working groups. Subsequent work has shown

however that for practical reasons the original layout could not be preserved in all details and some

headings have been merged, deleted or renamed and others have been added. Still, as far as possible,

we have tried to fit the contents of the national reports into the original structure and to keep its

headings and sub-headings.

The reports from the UK, Portugal, Romania and Sweden mainly comprise geological data on and

descriptions of mineralized areas in these countries. The EFG report presents a European inventory of

drill holes with temperatures in excess of 100°C, availability of data for these holes, and whether any

metal enrichment have been encountered at depth.

In this report we summarize and focus on data availability; for actual data, descriptions and

conclusions we refer to the individual working group reports (appendices 1.2.1 to 1.2.5). We will also

attempt to draw some conclusions on how the available information may be used to predict geological

and physical conditions relevant to the present task at greater crustal depths.

1.1 Country specific issues

Specific conditions or issues for each country in question have been noted in a few cases (see

appendices). As far as we understand, nothing that may be critical to the present task has been put

forward.

1.2 Goals

Our understanding of the formation of ultra-deep metallic mineral deposits is limited. Current 3D

metallogenic models typically focus on the upper 3 km of the crust. Mineralisation below this depth

has been of limited interest due to the challenges of extracting it with conventional mining and at

reasonable costs. The objective of this task is to highlight and categorize previously reported studies of

the uppermost crust of the Earth, e.g., from prospecting, deep drilling, and geophysical surveys,

integrating the outcomes of recent predictive models. We need to investigate the possible extension

of current metallogenic models to greater depths, and to understand knowledge gaps and limitations

that have to be overcome in order to confidently identify target s ites for a future CHPM facility.

Targeting sites will be the subject of the forthcoming task 6.2. Special attention has to be paid on the

relationship between mineralisation, deep seated faults and fault-zone/fracture geometry and the

structural setting of deposits. Deep seated faults and present and past tectonic conditions have an

impact on deep fluid flow. Hence, they may affect both local heat flow and the geometry and

composition of an ore deposit. The results of previous European research (like, e.g., ProMine,

Eurogeoresource) should be assessed and updated with information covering the target depth.


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2 Previous research and available data

The particular reports of the five working groups (see appendices) present available geological,

geophysical, drilling and other data related to mineralized areas in the European countries, with

special focus on England, Portugal, Romania and Sweden (figure 1). Some of the reports also provide

accounts of geological conditions, but varying in detail and extent.

It is tried to sum up information and accessibility about data and sources even in tabular form. The

report by the British Geological Survey (BGS; Appendix 1.2.1, chapter 10) contains a summary and

table of their data holdings. British data are freely or openly available. In most cases, however, they

only reflect conditions down to 600 to 1 000 m, or less.

Figure 1. Major ore deposits of Europe (after Weihed 2015), with the mining areas and their available data described in tasks 1.2.1 to 1.2.4 indicated (see appendices 1.2.1 to 1.2.4), i.e. , in the Southwest of

England, Southern Portugal, Northwestern Romania and Central and Northern Sweden

The reports from Portugal and Sweden (Appendix 1.2.2 and 1.2.4) include tables on databases held by

their national geological surveys, i.e., LNEG, and SGU. All of these data are accessible, either directly or

on request. In Appendix 1.2.5 we provide information on existing boreholes within Europe, where

temperatures of more than 100oC were measured and mineralisations being found. It should be

noticed that all kinds of data in accordance with INSPIRE in general are free of charge.


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2.1 Geology and geophysics, including dr i l l ing

The report from the BGS (Appendix 1.2.1) focuses on conditions in south-west England, i.e., connected

to six large granitic plutons in Cornwall, and contains a description of the geology, tectonic evolution

and physical properties of this area. Data exist in form of regional geological maps (1:50 000 scale) by

the BGS. Several comprehensive reviews on the geology are available as well as reports on

geochronology, isotopes and fluid inclusions. Wells for geothermal studies within a HDR project have

been drilled in the 1980s down to c. 2 600 m, but the majority of boreholes drilled for temperature

measurements is less than 100 m deep.

The Iberian Pyrite Belt (IPB) in Portugal and Spain constitutes an intensely mineralized part of the

crust, and has consequently been the subject of several studies as noted in the report from Portugal

(Appendix 1.2.2). The studies include general geological syntheses and evaluations of stratigraphy,

volcanism, structure and regional metamorphism, ore-related alterations, and facies architecture of

the ore-bearing volcano-sedimentary complex (VSC). Exploration drillings for metal deposits down to

more than 1 500 m have been performed in the IPB.

The report from Romania (Appendix 1.2.3) contains an extensive and detailed account of the tectonic

evolution and the geology of the country, specifically of the Bihor mountains, the Beius basin and the

Banatitic Magmatic and Metallogenic Belt (BMMB). It largely summarizes the relevant geological,

geophysical and other data for this task. As in the case of England, wells for geothermal studies have

been drilled in the Beius basin down to almost 2 600 m with the hot water used locally for heating

purposes.

The report from Sweden (Appendix 1.2.4) focuses on data availability. References are given to the

most recent geological descriptions, geophysical investigations and published papers. Sweden has four

ore-bearing districts: Bergslagen, the Skellefte field, northern Norrbotten and the Caledonides , of

which the first three ones are dealt with in the report. Geological maps with descriptions by SGU at

1:50 000 and 1:250 000 scales are available for most parts of these districts. Drilling down to almost

6 800 m has been performed in central Sweden and some tens of exploration boreholes are reaching

more than 1000 m in depth.

A short summary of the present knowledge and data of the above named ore districts, i.e., in the form

of keywords only, is given in tables 1 and 2. Figure 2 provides a general overview on major ore

deposits in Europe, based on the ProMine databases (Weihed 2015, Cassard et al. 2015).

2.2 Geometry and composition of ore deposits

The style of mineralisation in the areas of investigation, i.e., south-west England, the IPB of Portugal,

the BMMB of Romania and three mining districts of Sweden are described in the individual reports in

Appendix 1.2.1 to 1.2.4.


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2.3 Structural evolution, deep-seated faults and fracture zones, their a l ignment

Structural data and the structural evolution as well as data on the present stress field (measured stress

and directions) are documented for south-west England in Appendix 1.2.1. Similar data were acquired

in the IPB (Appendix 1.2.2), where structures and structural evolution have been evaluated by means

of detailed geological mapping, drilling and geophysical soundings. This information has been utilized

in 3D-modelling, particularly in areas with known mineralisations.

An extensive account of the tectonic and structural evolution in Romania and surrounding countries is

given in Appendix 1.2.3, while the situation in Sweden is discussed in Appendix 1.2.4 and relevant

publications noted there.

Figure 2. Main ore deposits of Europe, with their major ore content and size (class A, B, C) indicated,

according to the ProMine database (after Cassard et al. 2015).

2.4 Hydraul ic properties, deep fluid flow

Most data on crustal fluids in the European countries discussed here are available from uppermost

levels, usually extending down to a few 100 m depth. Data down to several 1000 m depth are fairly

uncommon. In general, the hydraulic conductivity and the magnitude of the fluid flow are very low at

deep levels.


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Table 1. Summarizing data about some of the ore districts of Europe that are the base for the present report


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Table 2. Summary of boreholes drilled in some of the European countries where temperature is above 100oC and mineralisations were identified (see even Appendix D1.5).


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Hydraulic properties of the upper crust in south-west England are described by using data from

structure and stress-field measurements (Appendix 1.2.1). Data from the IBP partly estimated from

pumping tests, are briefly discussed in the report from Portugal (Appendix 1.2.2).

An extensive description of the hydraulic properties in the Bihor Mountains and Beiuș basin in

Romania is given in Appendix 1.2.3. Hydraulic properties and deep fluid flow in various parts of

Sweden are discussed in Appendix 1.2.4. A large number of data were also provided from extensive

investigations done at study and research sites of the Swedish Nuclear Fuel and Waste Management

Company (SKB), though even here depth is limited.

2.5 Fluid composition, br ines, meteoric waters

Data on ancient ore-forming fluids (see Appendix 1.2.1) provide some frames on the character of

evidently metal-bearing fluids, and could be used for comparison to those on present day systems.

Fluids associated with granite-related vein-type mineralisations in south-west England were magmatic

in origin. They ranged from c. 280 to 400°C and contained between 5 and 15 wt% NaCl. Post-

magmatic vein mineralisations formed from cooler (c. 130°C) but more saline fluids with c. 26 wt%

NaCl.

The quality, e.g., of brines and waters at upper crustal levels varies considerably between countries

reported here. High values of total dissolved solids (TDS) are usually found at levels below 1000 m

depth.

Data on fluids in south-west England are extensive and well characterised in Appendix 1.2.1. The

existence of palaeobrines is well understood in the shallow sub-surface, but little is known for depths

>> 200 m. As in all cases when generalizing data, one has to be aware of bias in data owing to where

exploration or exploitation of commercially interesting minerals has occurred. There are currently no

data available on fluids in the IBP. However, these are expected to be provided in the near future

(Appendix 1.2.2). The composition of upper crustal fluids in the Bihor Mountains, Romania, is

described mostly by analyses of waters from springs (Appendix 1.2.3). Fluid characteristics from a

number of boreholes of various depths in Sweden are described in Appendix 1.2.4. The maximum

salinity in waters of 150 000 mg/l was reported from large depth of 5700 m in western central

Sweden, with their residence times estimated to hundreds of millions of years (Juhlin and Sandstedt

1989; Juhlin et al. 1998). The Cl-isotope composition of brines from 1000 m depth in coastal areas

indicates a residence time of approximately 1.5 Ma (Louvat et al. 1999).


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Figure 3. Temperature distribution at 1000 m depth in Europe (Schellschmidt and Hurter 2002)


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Figure 4. Generalised heat flow density map of Europe, based on the Atlas of Geothermal Resources in

Europe (after Hurter and Haenel 2002)

2.6 Thermal properties and heat flow

The geothermal heat flow in Europe ranges from less than 30 mW/m2 to values exceeding 150 mW/m2

(figure 4). Estimated temperature at 1000 m depth (figure 3) is partly related to the heat production

and indicates areas of interest for this project. South-west England and the western part of Romania

have relatively high temperatures at 1000 m depth and below.

Heat flow density in south-west England varies from 52 to 120 mW/m2 as given in Appendix 1.2.1. The

temperature gradient from borehole data was calculated to 26 to 35oC/km and temperature at 5000

m depth estimated to 185–220°C.

In the IBP, heat flow density was estimated to 65–85 mW/m2 and temperature extrapolated to about

130oC at 5000 m depth (Appendix 1.2.2). As for Romania, in the BMMB heat flow density reaches 105

mW/m2 and temperature at 3000 m depth is 80–90oC. These data and further ones on heat

production and thermal conductivity from different parts of Romania are described in Appendix 1.2.3.


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A description of data on thermal properties of the uppermost crust in Sweden is available in Appendix

1.2.4. Heat flow in the mining districts is varying between 50 and 60 mW/m2 and the geothermal

gradient is low, around 17oC/km.

Appendix 1.2.5 summarizes information on boreholes in more than 20 European countries, where

temperature was reported to be above 100oC and mineralization occurs. In future work these data

need to be extended.

2.7 Current metal logenic models (2D- and 3D-)

The formation of mineralisations according to their magmatic stage, with primarily tin and copper

deposits, is discussed in the report for south-west England (Appendix 1.2.1). Mineralisations of the IPB

are volcanogenic massive sulphide (VMS) deposits and described in Appendix 1.2.2.

The most important mineralisations in Romania are associated with the Banatitic Magmatic and

Metallogenic Belt (BMMB), a 900 km long and 30 – 70 km wide zone. The Bihor Mountains are a part

of this belt and of the Northern Apuseni Mountains and contain ore deposits of brucite, borate and

skarn (Appendix 1.2.3). Sweden has an abundance of mineralisations representing most styles of ore-

formation (Appendix 1.2.4).


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3 Identifying target sites for future CHPM

3.1 Extending existing models to greater depth, integrating data down to 7 km

Ore prospecting campaigns in the European countries, e.g., like in Portugal and Sweden, have not only

increased by number but even by their depth of investigation. Efforts are undertaken looking deeper

into the sub-surface and enhancing resolution for detecting mineralized zones, ore bodies and imaging

faults, fracture zones and lithological contrasts. This is not only based on using traditional potential

field methods, like gravity and magnetic methods, but also applying deep electromagnetic-, e.g.,

magnetotelluric (MT) and reflection seismic methods. Because of an often suitable contrast in

electrical resistivity between the host rock and the mineralized zone, MT and especially AMT

measurements, make it possible to identify such zones, though depth resolution may not be satisfying.

Reflection seismics, instead, can provide high-resolution images of the underground and sufficient

depth of investigation. For Sweden, several studies where high resolution seismics was used for

mineral exploration and site characterization were published, e.g., Juhlin and Palm (1999), Malhemir

et al. (2006, 2007, 2009a, b, 2011), Tryggvason et al. (2006), Schmelzbach et al. (2007). The limiting

factor in applying high resolution reflection seismic waves, and, in a powerful combination, also

electromagnetics (AMT) to screen the sub-surface is the economy of such investigations. Thus,

exploration depth is constrained by the accessibility of an ore deposit at depth by direct mining.

Much of the information of the upper crust in SW England relates to the upper 1000 m, except for the

Carnmellenis granite, where a HDR project provided better insight into the upper crust (see Appendix

1.2.1). The granite bodies of Cornwall are estimated to be of tabular shape, reaching down to about 3

– 4 km, or even much deeper. But, deep exploration data, in excess of 1000 m in depth are rare. In

Romania, for the BMMB not much is reported from deep geophysical studies, beside from magnetic

and gravity surveys. However, without additional data from reflection seismics these potential

methods suffer from limited resolution in structures and depth.

With the present information available on the sub-surface of the areas under consideration, i.e., from

geology, geophysics and boreholes, it is hard to properly extrapolate structures to greater depth. The

investigations reported from Sweden (cf. Appendix 1.2.4, fig. 12) show that considerable efforts need

to be undertaken in geologically complex areas to properly acquire data, i.e., preferably having 3D-

instead of 2D seismic surveys – though again economic issues will limit this precondition.

3.2 Knowledge gaps and l imitations

As reported here, geological and geophysical data are in most cases only available for the uppermost

c. 1000 m of the crust, but rare further down. Locally, boreholes to greater depths (<c. 3 000 m; in

England and Romania) have been drilled, while in Sweden a hole down to almost 6 800 m exists.

This project, CHPM2030, requires the prediction of structures and lithology in complex environments

at depth down to about 4–7 km, and estimating temperature, metal content, fluid chemistry and flow

in the bedrock. Predicting the stress field, fracture geometry and permeability at depth in the

crystalline bedrock is of crucial importance and highly challenging. With the present knowledge and


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data available this task is not easy to fulfil. For pilot areas within CHPM2030, further intensive multi-

disciplinary studies must be considered, e.g., three-dimensional electromagnetic and seismic surveys,

as well as better predictions of temperature, heat flow and permeability at depth. The 3D integration

of geological and geophysical results will then better allow for planning and conducting of exploration

and possibly later-on production drillings.


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4 Discussion and concluding remarks

The reports of the four nation-based working groups from the UK, Portugal, Romania and Sweden

show that the general geology of the chosen area(s) in each country is well known and documented

(appendices 1.2.1 to 1.2.4). In general, this is also the case for existing mineralisations and their styles

of formation. A significant amount of data underpins this knowledge base, the majority of which is

freely, or openly available. However, there are limitations. The knowledge is often restricted to the

upper 1 000 m (or less) of the crust. Locally, where deep drilling has been performed, the conditions

may be evaluated to greater depths. The availability of data has significant implications regarding the

accuracy of modelled conditions in an enhanced geothermal system (EGS) at greater depths.

Available data from deeper levels are fairly infrequent. Most of the available data originate from

governmental organisations which are obliged to provide data. On the other hand, data from mining

companies are in many cases considered to be privately owned and not available. Properties and

description of metadata (e.g., location, sampling methods), could be limiting factors for interpretation

of data.

Acknowledgements

The compilation of a report on existing data of several mining districts in Europe needs many helpful

hands. We acknowledge the support of our colleagues at our home institutions, national universities

and mining and exploration companies. Tobias Weisenberger is thanked for critically reading the

manuscript.

References

For practical reasons, we do not duplicate references here; instead, the reader is referred to the

references given in the appendices.

Other sources / Web links

EuroGeoSurveys (EGS), web links there, like, e.g., for Eurare, EuroGeoSource, Minerals4EU, Promine,

ThermoMap (www.eurogeosurveys.org).

http://www.eurogeosurveys.org/

CHPM2030 DELIVERABLE D1.2 APPENDIX 1.2.1

REPORT ON DATA AVAILABILITY:

SOUTH WEST ENGLAND

Summary:

This report provides an overview of geoscientific data and information relating to South West

England, with a particular focus on its geology, structure, stress-field characteristics,

mineralisation and previous geothermal research in the region.

Authors:

Richard A Shaw, economic geologist, Eimear Deady, economic geologist, Keith Bateman,

geochemist, Paul Lusty, economic geologist (British Geological Survey)

CHPM2030 DELIVERABLE 1.2 APPENDIX 1.2.1

(A1.2.1) 2 / 44

Table of contents

Executive summary ............................................................................................................................................ 5

1 Preface ...................................................................................................................................................... 7

2 Introduction .............................................................................................................................................. 8

3 Geology ..................................................................................................................................................... 9

3.1 Summary ........................................................................................................................................ 12

3.2 How South West England can positively contribute to the aims of CHPM2030: ............................ 12

3.3 Limitations in our current understanding of the geology of South West England: ......................... 12

4 Fluids ....................................................................................................................................................... 13

4.1 Summary ........................................................................................................................................ 16


4.3 Limitations in our current understanding of fluids in South West England: ................................... 16

5 Mineralisation ......................................................................................................................................... 17

5.1 Historical production ...................................................................................................................... 17

5.2 Mineralisation in South West England ............................................................................................ 18

5.3 Summary ........................................................................................................................................ 21


5.5 Limitations in our current understanding of the mineralisation in South West England: ............... 21

6 Structure and stress-field measurements ............................................................................................... 22

6.1 Summary ........................................................................................................................................ 24

6.2 How South West England can positively contribute to the aims of the aims of CHPM2030: ......... 24

6.3 Limitations in our current understanding of the stress field in South West England: .................... 24

7 Deep sub-surface temperatures in South West England ........................................................................ 25

7.1 United Kingdom overview .............................................................................................................. 25

7.2 South West England overview ........................................................................................................ 26

7.3 Summary ........................................................................................................................................ 27


7.5 Limitation in our current understanding of deep sub-surface temperatures in South West England:

27

8 Hot Dry Rock (HDR) research programme ............................................................................................... 28

8.1 Volume 3: The use of natural radioelement and radiogenic noble gas dissolution for modelling the

surface area and fracture width of a Hot Dry Rock system (Andrews et al. 1989) ...................................... 30

8.2 Volume 4: Fluid circulation in the Carnmenellis granite: hydrogeological, hydrogeochemical, and

palaeofluid evidence (Smedley et al. 1989) ................................................................................................. 30

8.3 Volume 5: Mineralogy and geochemistry of the Carnmenellis granite (Bromley et al. 1989) ........ 30

8.4 Volume 6: Experimental investigation of granite-water interaction (Savage et al. 1989) .............. 31

8.5 Volume 7: Geochemical prognosis for a Hot Dry Rock system in South West England (Richards et

al. 1989) ....................................................................................................................................................... 32

8.6 Summary ........................................................................................................................................ 32


8.8 Limitation in our current understanding of South West England: .................................................. 32


(A1.2.1) 3 / 44

9 Data holdings at BGS ............................................................................................................................... 33

9.1 Summary ........................................................................................................................................ 33


9.3 Limitations in our current understanding of South West England: ................................................ 33

10 Conclusion ............................................................................................................................................... 36

11 References .............................................................................................................................................. 37

List of figures

Figure 1. Simplified geological map of South West England showing the distribution of sedimentary basins

and the location of the granites (re-drawn from BGS mapping data and Shail and Leveridge, 2009) ............... 9

Figure 2. Map showing the principal mineralogical and textural variations in the Cornubian Batholith. It

combines subdivision into biotite and lithian-mica granites with a textural scheme based primarily on mean

matrix grainsize and the size and abundance of alkali feldspar megacrysts – compiled from Exley and Stone

(1964, 1982) Stone and Exley (1985), Hawkes and Dangerfield (1978), Dangerfield and Hawkes (1981), Exley

et al. (1983), Floyd et al. (1993), Manning et al. (1996), Manning (1998) and Shail et al. (2014). In-set map

shows the distribution of granite ages: Dartmoor, St Austell and Land’s End (in purple) are <286 Ma, whereas

Bodmin, Carnmenellis and Isle of Scilly (in yellow) are older (>290 Ma) ......................................................... 11

Figure 3. Schematic diagram illustrating fluid flow regimes in relation to emplacement of the Carnmenellis

granite. (a) Expulsion of magmatic fluids forming Sn-W greisens and generation of hydrothermal convection

in overlying groundwaters. (b) Leaching of metals and sulphur from the host rocks. Cooling of the system

permits meteoric waters to pass down into the granite pluton. (c) Main stage, polymetallic lodes form in the

roof zone of the granite pluton by expulsion of magmatic fluids. (d) Meteoric waters circulate through the

granite as the system cools. Cu-Zn sulphides are deposited in a series of lodes (re-drawn after Smedley et al.,

1989) ................................................................................................................................................................ 15

Figure 4. Overview of the evolution of mineralising fluids in South West England (after Leveridge et al., 1990)

......................................................................................................................................................................... 20

Figure 5. Map of the distribution of major NW-SE-trending faults and granite bodies in South West England

(drawn from BGS mapping data) ..................................................................................................................... 22

Figure 6. Principal stress orientation and magnitude in the Carnmenellis granite as determined by in-situ

hydraulic fracture tests at the Rosemanowes HDR test site (re-drawn from Pine and Batchelor, 1984) ........ 23

Figure 7. Heat flow map of the UK (after Busby, 2010) .................................................................................... 25

Figure 8. Revised estimated granite-related average temperatures (°C) at a depth of 5 km and the percentage

increases (in brackets) over previously published estimates. Locations of five towns, are shown in blue; PEN =

Penzance; StI = St Ives; CAM = Camborne; RED = Redruth and; StA = St. Austell (after Busby and Beamish,

2016) ................................................................................................................................................................ 26

Figure 9. Location of the Rosemanowes HDR test site in relation to the Carnmenellis granite outcrop (re-

drawn from Edmunds et al., 1989) .................................................................................................................. 28

Figure 10. A schematic diagram showing the configuration of the 2 and 2.5 km test wells at the

Rosemanowes HDR test site (re-drawn from Edmunds et al., 1989) ............................................................... 29


(A1.2.1) 4 / 44

List of tables

Table 1. Summary of fluid inclusion data for mineralising fluids (Smith et al., 19961 and Gleeson et al., 20012).

......................................................................................................................................................................... 13

Table 2. Summary of mine water compositions (n.r., ‘not reported’) .............................................................. 14

Table 3. Estimated total mineral and metal production from South West England. After Dines (1956),

Alderton (1993) and South Crofty PLC (1988-1998). Adapted from LeBoutillier (2002) .................................. 17

Table 4. Summary of mineralisation styles in the South West England (Cornubian) orefield (adapted from

Andersen et al. 2016). ...................................................................................................................................... 19

Table 5. Summary of datasets pertinent to CHPM2030 held by the BGS (continued on next page) ............... 34


(A1.2.1) 5 / 44

Executive summary

This report provides a summary of key information available for South West England, which is relevant for

development of enhanced geothermal systems in the region. South West England is a geologically complex

region with a long and significant history of metal mining, producing primarily tin (c. 2.8 million tonnes) and

copper (c. 2 million tonnes). The geology of the region is largely the result of Variscan tectonics and

associated felsic magmatism. The current surface expression of the Cornubian Batholith comprises six large

granitic plutons. From west to east these are: the offshore Isles of Scilly (120 km2), Land’s End (190 km2),

Carnmenellis (135 km2), St Austell (85 km2), Bodmin (220 km2), and Dartmoor (650 km2). These granite

bodies were intruded into a series of Devonian (410–355 Ma) green schist facies metasedimentary rocks,

locally known as ‘killas’ during the late Carboniferous and early Permian (295–270 Ma). The granites of South

West England are texturally and compositionally complex, although broadly they comprise peraluminous, S-

type granites of the two-mica variety. They are enriched in elements that include K, F, B, Li, Sn, Th, U and Rb.

However, it is their enrichment in K, Th and U that is responsible for their heat-production via radioactive

decay.

Mineralisation in South West England is wide-spread and can be broadly divided on the basis of its timing

relative to granite emplacement as: (1) pre-granite orebodies of the sedimentary-exhalative type, and shear-

zone hosted Au-Sb type; (2) granite-related mineralisation, comprising greisens and sheeted vein complexes,

and polymetallic sulphide lodes and; (3) post-granite mineralised Zn-Pb-Ag veins (so called crosscourses).

Fluids associated with granite-related mineralisation are magmatic in origin, and ranged in temperature from

about 400°C for Sn-W greisens to about 280°C for Sn-Cu polymetallic lodes, with salinities ranging between 5

and 15 wt% NaCl. Post-granite mineralisation is dominated by Pb and Zn rather than Sn and Cu, and formed

from lower temperatures fluids (c. 130°C), with higher salinities of about 26 wt% NaCl. Warm (up to 55°C),

high-salinity groundwaters have been found at depths of up to 820 metres depth, primarily issuing from

crosscourses and lodes in mines at the northern edge of the Carnmenellis granite. These flows occur in

mines in both the granite and in the killas. Some of the crosscourse flows have been discharging for more

than 30 years, suggesting that a large reservoir of saline, thermal water exists at depth.

The south-west of England is structurally complex with at least three different episodes of deformation

identified. Permeability in the south-west is fracture dominated. Therefore, it is the large NW-SE-trending

fault structures that are potentially most important for enhanced geothermal systems in terms of fluid flow.

Principal stress orientations are about 30° off parallel from that of the NNW-SSE and ENE-SWS-trending

joints sets observed in the Carnmenellis granite. The maximum in-situ stress (σH) is about 70 MPa in the

NNW-SSE direction, whilst the minimum in-situ stress (σh) is about 30 MPa in an ENE-WSW direction.

Previous geothermal research in the south-west of England peaked between the 1970s and 1990s. The

south-west region was of interest because of the high heat flows present in the Cornubian granites (c. 115–

139 mWm-2). These high heat flow values suggest high temperatures (c. 185–220°C) at depths of 5 km or

more.

In 1984 an extensive programme of work, funded by the UK Department of Energy (DEn) and the

Commission of the European Communities (CEC), was undertaken by the British Geological Survey (BGS) to

assess the UK’s geothermal potential. Over the same time period (1977–1984) the Camborne School of

Mines (CSM) was assessing the feasibility of creating HDR geothermal systems at a test site at the

Rosemanowes quarry, on the Carnmenellis granite, in Cornwall. It was assumed that the behaviour and

characteristics of a HDR system could be modelled using geochemistry, geophysics and physical properties


(A1.2.1) 6 / 44

testing. Between 1985 and 1989 the Department of Energy and the Commission of the European

Communities funded a detailed geochemical investigation of the HDR site at Rosemanowes. These

investigations were undertaken by the BGS, the then NERC Isotope Geology Centre (NIGC), the University of

Bath (UoB) and CSM. In 1987 an informal working group (the UK Hot Dry Rock Geochemistry Group) was

established to align the geochemical programme more closely with the work being undertaken by CSM at

the Rosemanowes test site.

In summary a huge amount is already known about the geology, mineralisation fluid history and geothermal

potential of South West England. A significant body of data underpins this knowledge base, the majority of

which is freely, or openly available. However, there are limitations. For example, much of this data, with the

exception of the HDR datasets, only relates to the upper 1,000 m of the crust. This has significant

implications regarding the accuracy of modelled conditions in an enhanced geothermal system (EGS) at

greater depths. There are also ‘gaps’ in the data (e.g. very limited deep-geophysical data), and some data

sets have not been updated since their creation in the 1970s and 1980s.


(A1.2.1) 7 / 44

1 Preface

This report is a published product of the ‘CHPM2030’ project – an EC-funded, Horizon2020 project which

aims to develop a novel and potentially disruptive technology solution that can help satisfy European needs

for energy and critical metals in a single interlinked process. Working at the frontiers of geothermal

resources development, minerals extraction and electro-metallurgy, the project aims to convert ultra-deep

metallic mineralisation into ‘orebody-enhanced geothermal systems’ that will serve as a basis for the

development of a new type of facility for ‘Combined Heat, Power and Metal extraction’ (CHPM).

The project will help provide new impetus to geothermal development in Europe by investigating previously

unexplored pathways at low-TRL. This will be achieved by developing a roadmap in support of the pilot

implementation of such system before 2025, and full-scale commercial implementation before 2030. This

will include detailed specifications of a new type of future EGS facility that is designed and operated from the

outset as a combined heat, power and metal extraction system.

In the technology envisioned, the metal-bearing geological formation will be manipulated in a way that the

co-production of thermal energy and metals will be possible. As part of this, we will investigate how fluid

chemical conditions can be optimised to facilitate recovery of specific metals, anticipating variable market

demands in the future. Four geographical areas have been chosen for assessment based on pre-existing data

and potential for CHPM development in mineralised areas in the United Kingdom (UK), Portugal, Romania

and Sweden. This report summarises information relevant to the UK.

The project aims to provide proof-of-concept for the following hypotheses:

1. The composition and structure of orebodies have certain favourable characteristics that could be used to

our advantage when developing an EGS;

2. Metals can be leached from the orebodies in high concentrations over a prolonged period of time and

may substantially influence the economics of EGS;

3. The continuous leaching of metals will increase system’s performance over time in a controlled way and

without the need to use high-pressure reservoir stimulation, minimising the potential detrimental

impacts of both heat and metal extraction.


(A1.2.1) 8 / 44

2 Introduction

During the last 50 years geothermal energy research in the UK has been limited, partly due to a lack of high-

enthalpy resources, but also because of the availability of cheap fossil fuels during the 1980s and 1990s.

Research has focussed on three main aspects: (1) a nationwide appraisal of heat flow; (2) energy generation

from hot-brines in deep, hyper-saline aquifers (HSA) and; (3) energy generation from enhanced geothermal

systems (EGS) in hot dry rocks (Busby, 2010).

Heat flow measurements (Lee et al., 1987; Downing and Gray, 1986; Rollin, 1995; Rollin et al., 1995 and;

Barker et al., 2000) place UK background heat flow at about 52 mW m2, with elevated values associated with

buried granites in north-eastern England and radiogenic granites in South West England. The average UK

geothermal gradient is approximately 26°C km-1, although locally it can exceed 35°C km-1.

The radiogenic granites of South West England were assessed for their HDR geothermal energy potential as

part of the HDR project during the 1970s and 1980s. This programme of work was largely undertaken by the

Camborne School of Mines to assess the performance of an EGS in the Carnmenellis granite, in South West

England. The test site operated a set of deep (between 2–2.5 km) boreholes to assess the feasibility of

developing a full-scale commercial HDR system at about 5–6 km depth.

South West England was chosen as a potential pilot study site for the CHPM2030 project because of the

large amount of data that are available for South West England, the region’s status as a historically important

orefield, and because of the history of geothermal research in the region.


(A1.2.1) 9 / 44

3 Geology

The geology and metallogenesis of South West England is complex and has been the subject of extensive

scientific research for more than two centuries. It was during the eighteenth century (c. 1778) that William

Pryce first attempted to synthesise the geology, mining practices and metallurgy of the region. A number of

important papers followed in the early to mid-nineteenth century (Phillips, 1814; De La Beche, 1839;

Henwood, 1843) that sought to explain the role of granite and circulating fluids in the formation of South

West England’s mineral deposits. This extensive metallogenic province, covering the county of Cornwall and

part of the county of Devon from Land’s End to Dartmoor, a distance of some 150 km is termed the

‘Cornubian Orefield’. Significant advances were made during the twentieth century in understanding the

formation of the Cornubian Orefield, with the publication of numerous papers by Dines (1934 and 1956) and

Hosking (1950, 1951, 1952, 1964, and 1969). Geoscience research during the past forty years has sought to

refine many of the earlier theories and concepts by the application of geochronology (Chesley et al., 1993;

Chen et al., 1993; Clark et al., 1993; Clark et al., 1994; and Darbyshire, 1995), isotope studies (Rouse and

Colman, 1976; Darbyshire and Shepherd, 1994; and Shail et al., 2003) and fluid inclusion research

(Williamson et al., 1997; Gleeson et al., 2000; 2001; Williamson et al., 2000; and Müller and Halls, 2005).

Figure 1. Simplified geological map of South West England showing the distribution of sedimentary basins

and the location of the granites (re-drawn from BGS mapping data and Shail and Leveridge, 2009)

Regional geological mapping by the British Geological Survey at 1:50 000 scale, and airborne geophysical (i.e.

magnetic and radiometric) and remote sensing (i.e. LiDAR) surveys, flown as part of the TELLUS South West

project, have further contributed to the geological knowledge base. Comprehensive reviews of the geology


(A1.2.1) 10 / 44

of South West England can be found in Selwood et al. (1998), LeBoutillier (2002) and Shail and Leveridge

(2009), and references therein.

A brief chronology of major geological events in South West England, from oldest to youngest, includes: (1)

The development of a series of middle Palaeozoic (410–345 Ma), east-west trending volcano-sedimentary

basins (from east–west these are the: North Devon Basin; Culm Basin; Tavy Basin; South Devon Basin; Looe

Basin and; Gramscatho Basin) (Figure 1) that have been inverted, deformed and subjected to low-grade

metamorphism (Parker, 1989; Shail, 2014); (2) Variscan continental collision, during the mid-Carboniferous

(331–329 Ma), resulted in significant crustal shortening and the development of NNW-trending thrust sheets

(Parker, 1989; Shail, 2014); (3) Crustal extension and orogenic collapse during the late Carboniferous and

lower Permian that resulted in extensive granitic magmatism (295–270 Ma) and associated hypothermal

(300–600°C) Sn-W greisens, and mesothermal (200–300°C) Sn-Cu mineralisation hosted by E-W-trending

mineral lodes. Following granite emplacement widespread Pb-Zn mineralisation developed in N-S-trending

crosscourses, many of which are re-activated NNW-trending thrust sheets (Parker, 1989; LeBoutillier, 2002;

Shail et al., 2014) and; (4) Cyclic periods of uplift, erosion and sedimentation throughout the Jurassic and

Cretaceous (Parker, 1989; Shail et al., 2014) resulting in the current landscape (e.g. exposure of granite roof

zones at the existing land surface).

Emplacement of the Cornubian batholith into largely Devonian sedimentary rocks caused large-scale heating

and thermal alteration. These metamorphic rocks in South West England are locally known as ‘killas’.

Although these rocks are not economically important in themselves, fractures within them host a significant

proportion of the region’s mineral deposits (e.g. polymetallic mineral veins, or ‘lodes’). The ‘killas’ comprises

a series of Devonian (410–355 Ma), marine deposited sandstones, siltstones, mudstones and rare

carbonates that were regionally metamorphosed to sub-green schist facies during the Variscan Orogeny. As

a result of granite emplacement, the low-grade regional metamorphism has been locally overprinted by

higher-grade contact metamorphism, to produce a series of aluminosilicate and/or cordierite-bearing slates

(Selwood et al., 1998).

The current surface expression of the Cornubian Batholith is six large granite plutons. From west to east

these are: the offshore Isles of Scilly (120 km2), Land’s End (190 km2), Carnmenellis (135 km2), St Austell (85

km2), Bodmin (220 km2), and Dartmoor (650 km2) (Figure 1). The subsurface extent of the Cornubian

Batholith is estimated to be about 250 km in length and has an approximate width of between 40 and 60 km

(Willis-Richards and Jackson, 1989; Scrivener, 2006). However, there is uncertainty about the true size of the

Cornubian Batholith because current models are based on a small amount of data (e.g. gravity

measurements and a very limited number of deep drill holes). Similarly there is some uncertainty about the

true thickness and shape of the granite plutons. 2D-gravity modelling of the Carnmenellis, St Austell and

Bodmin granites indicates they are tabular bodies with an estimated thickness of between three and four

kilometres, whilst the larger Dartmoor pluton is estimated to be about nine kilometres thick (Taylor, 2007).

However, seismic refraction data suggest that the depth of the base of the batholith (i.e. its lower contact

with the killas) is variable, ranging from about seven and eight kilometres beneath the Bodmin and

Carnmenellis granites, respectively, to about ten kilometres beneath the Dartmoor granite (Brooks, 1984;

Shail et al., 2014).

Radiometric dating (U-Pb in monazite and zircon) suggests that the extensive granitic magmatism observed

in South West England occurred over an about 20-million-year period, between about 293 Ma and 274 Ma,

although separate intrusive episodes can be identified in some of the individual plutons (Chen et al., 1993;

Chesley et al., 1993; Clark et al., 1994). In terms of age, the plutons can be broadly divided into two groups:


(A1.2.1) 11 / 44

(1) the older (>290 Ma) Bodmin Moor, Isles of Scilly and Carnmenellis granites and; (2) the younger (<286

Ma) Land’s End, St Austell and Dartmoor granites (Figure 2).

Compositionally the granites are all peraluminous, S-type granites that are enriched in elements such as K, B,

F, Li, U, Th, Sn, Rb and Pb. An interesting feature of Cornubian granites is their high uranium content (with an

average of about 12 ppm for all plutons), which is largely controlled by the distribution of accessory minerals

such as uraninite and monazite (Chappell and Hine, 2006; Scrivener, 2006). Importantly it is the radioactive

decay of uranium, thorium and potassium in the Cornubian granites that is responsible for their high heat

production through radioactive decay (Chappell and Hine, 2006).

Figure 2. Map showing the principal mineralogical and textural variations in the Cornubian Batholith. It

combines subdivision into biotite and lithian-mica granites with a textural scheme based primarily on mean

matrix grainsize and the size and abundance of alkali feldspar megacrysts – compiled from Exley and Stone

(1964, 1982) Stone and Exley (1985), Hawkes and Dangerfield (1978), Dangerfield and Hawkes (1981), Exley

et al. (1983), Floyd et al. (1993), Manning et al. (1996), Manning (1998) and Shail et al. (2014). In-set map

shows the distribution of granite ages: Dartmoor, St Austell and Land’s End (in purple) are <286 Ma, whereas

Bodmin, Carnmenellis and Isle of Scilly (in yellow) are older (>290 Ma)


(A1.2.1) 12 / 44

The granites of South West England can be categorised mineralogically into three broad groups: (1) biotite

granite; (2) topaz granite; and (3) tourmaline granite. However, minor variants also exist, including Li-mica

granite and fluorite granite (Exley et al., 1983; Floyd et al., 1993; Manning et al., 1996). Textural variations

are also used to distinguish sub-classes of the granites e.g. fine-grained tourmaline granite (Manning et al.,

1996) (Figure 2). The older granites (Bodmin Moor, Isles of Scilly, and Carnmenellis) can be distinguished

from the younger granites (Land’s End, St Austell and Dartmoor) by their texture, composition

(peraluminosity), isotopic signature (εNd) and rare earth element (REE) patterns. These differences may

reflect increased mantle-melting and possibly increased amounts of crustal melting during formation of the

younger granites, probably in response to higher temperatures in the lower crust. However, it remains

unclear why temperatures increased, and if this change was transitional, or an abrupt change in response to

a discrete tectonic event (Stone, 1995; 1997; 2000a; 2000b; Shail et al., 2014).

3.1 Summary

The region has been studied for more than 200 years and thus a large amount of data exists that describes

the relationship between magmatism and mineralisation. Complimentary geological mapping and airborne

geophysical surveys have further refined the interpretation of the geological evolution of the region. The

abundance of magmatism and mineralisation across South West England warrants its status as a globally

significant metallogenic province.

3.2 How South West England can positively contribute to the aims of CHPM2030:

Extensive body of academic literature.

Good understanding of the geological evolution of the region.

Continuous digital geological mapping at 1:50,000 scale.

Complimentary regional datasets (e.g. LiDAR, airborne geophysics, geochemistry, etc.).

3D model of the geology at 1:625,000 scale.

3.3 Limitations in our current understanding of the geology of South West England:

The majority of the primary data that exists is related to the shallow sub-surface (<1,000 m, and often <200

m). There has also been no regional deep geophysical investigation. As a consequence, this presents

uncertainty in terms of extrapolating information and data at surface to any significant depth.


(A1.2.1) 13 / 44

4 Fluids

Academic research in South West England during the past 30 years has focussed on the nature of

mineralising fluids, and their role in metal transport and ore deposit formation. Fluid inclusion (i.e. fluids

trapped during mineral growth) studies have been invaluable in revealing the composition (salinity),

temperature and in some cases the pressure of the mineralising fluids. Complimentary stable isotope studies

(e.g. O, H, He and S) have also provided useful information on the source of the mineralising fluids (e.g. He

signatures suggest a mantle-derived volatile component) (Shail et al., 2003). Studies of shallow groundwaters

(down to c. 100 m), as part of the HDR programme have provided insights into water-rock interaction over

short time intervals and at shallow depths. Similar studies of deep, thermal spring waters from disused mines

provide information on fluid circulation and mixing. When combined these data (e.g. shallow groundwater

and mine water composition, and fluid inclusion studies) have enabled important conclusions to be drawn

regarding palaeofluid circulation in both the granites and country rocks of South West England (Smedley et

al., 1989).

Broadly two dominant fluid types have been implicated in the formation of mineralisation in South West

England:

(1) Moderate to high salinity (NaCl+CO2), high temperature magmatic fluids that produced the granite-

related mineralisation (e.g. polymetallic Sn-Cu lodes); and

(2) High salinity (NaCl+CaCl2), lower temperature basinal fluids that formed the younger, post-magmatic

mineralisation (e.g. crosscourses) (Table 1).

Mineralisation style Temperature Salinity Composition

Greisen1 450–350°C 5–10 wt% NaCl±CO2

Polymetallic lode (Sn-Cu)2 280–200°C 3–15 wt% NaCl

Polymetallic lode (Pb-Zn)2 c. 220°C 0–5 wt% NaCl

Crosscourse2 c. 130°C 26 wt% NaCl±CaCl2

Table 1. Summary of fluid inclusion data for mineralising fluids (Smith et al., 19961 and Gleeson et al., 20012).

Stable isotope studies (i.e. Cl, O, H, He and S) on fluids taken from inclusions in the mineralisation have

provided useful insights in to the origin of mineralising fluids. For example, isotopic studies of main stage,

polymetallic lodes indicate that mineralising fluids were principally magmatic in origin, whilst fluids

associated with later crosscourses are distinctly non-magmatic, having a strong sediment-derived fluid

signature (Wilkinson et al., 1995; Gleeson et al., 1999; Banks et al., 2000; Shail et al., 2003).

Warm (up to 55°C), high-salinity groundwaters have been found at depths of up to 820 metres, primarily

issuing from crosscourses and lodes in mines at the northern edge of the Carnmenellis granite. These flows

occur in mines in both the granite and in the killas. Some of the crosscourse flows have been discharging for

more than 30 years, suggesting that a large reservoir of saline, thermal water exists at depth (Smedley et al.,

1989). These deep spring waters 31–55°C, mildly acidic to neutral (pH 5.4–7.7), and compositionally they are

dominated by Na, Ca and Cl (Smedley et al., 1989) (Table 2). Stable oxygen (δ18O) and hydrogen (δ2D) isotope

studies indicate that these waters are not derived from seawater, but are more likely diluted palaeobrines


(A1.2.1) 14 / 44

which have flowed through crosscourse structures within the granite and killas. Their chemical and isotopic

signatures also indicate mixing and dilution by circulation of local meteoric water (Alderton and Sheppard,

1977; Smedley et al., 1989).

Parameter South Crofty

(420 level)

South Crofty

(420 level) Wheal Jane Clifford United

Source Smedley et al., 1989 Alderton and Sheppard, 1977

Depth (m) 690 690 198 448

pH 6.79 5.38 7.70 n.r.

Temperature (°C) 45.3 34.3 31.5 52

Total dissolved solids 14,099 10,454 9,934 9,189

Na 3,210 1,890 2,073 2,043

K 138 66.8 127 111

Mg 51.6 94.8 29.5 32

Ca 1,670 1,630 1,326 1,166

Cl 8,750 6,500 6,110 5,628

SO4 107 240 118 124

HCO3 n.r. n.r. 23.8 n.r.

Table 2. Summary of mine water compositions (n.r., ‘not reported’)

Low salinity, shallow groundwaters from within the granite and killas show considerable compositional

overlap. However, slight differences can be observed in both the major cation (i.e. Ca, Mg, Na and K) and

anion (i.e. HCO3, SO4, Cl and NO3) contents of these waters. Granite-related shallow groundwaters are more

acidic (pH 4.3–6.9) and are dominated by Na, K and Cl, whilst killas-related groundwaters are more alkaline

(pH 4.9–8.0), and have compositions dominated by Ca, Mg and HCO3. The higher overall concentration of

elements (e.g. Ca, Mg, Cl, etc.) in killas-related groundwaters suggests that that the killas is more reactive, or

possibly more soluble, than the granite. The abundance of minerals such as calcite, dolomite, chlorite and

clays in the killas may account for these higher concentrations by dissolution and precipitation, and ion

exchange reactions. Element enrichment and depletion patterns suggest that shallow groundwater

compositions are strongly controlled by lithology. For example, granite-related waters typically have higher

Ba and Rb contents, which likely reflects dissolution of alkali feldspar (Smedley et al., 1989; Smedley and

Allen, 2004).

Previous studies suggest that palaeo-fluid flow in and around the Carnmenellis granite can be divided in to

four main stages (Figure 3): (1) Expulsion of early magmatic fluids associated with the emplacement of the

granite, which led to the formation of sheeted Sn-W greisens in the granite roof zone and overlying

metasedimentary rocks. Hydrothermal convection of formation waters starts to occur in response to the

thermal anomaly created by the granite emplacement. (2) Copper, zinc and sulphur are leached from the

host rocks. Formation waters are drawn down through the granite as the system begins to cool, resulting in


(A1.2.1) 15 / 44

the deposition of Cu-Zn-sulphides in veins. (3) Main-stage, polymetallic lodes are emplaced within the

granite roof zone by further expulsion of magmatic fluids. (4) Formation waters start to circulate through the

granite in response to cooling of the system, resulting in the deposition of Cu-Zn-sulphides in steeply dipping

fissures (Smedley et al., 1989). Post-magmatism basinal brines circulate through N-S-trending structures

within the granite and killas, mixing with meteoric waters. These fluids deposited Pb-Zn-rich mineralisation

within the so called crosscourse veins (Scrivener et al., 1994; Gleeson et al., 2000; 2001).

Figure 3. Schematic diagram illustrating fluid flow regimes in relation to emplacement of the Carnmenellis

granite. (a) Expulsion of magmatic fluids forming Sn-W greisens and generation of hydrothermal convection

in overlying groundwaters. (b) Leaching of metals and sulphur from the host rocks. Cooling of the system

permits meteoric waters to pass down into the granite pluton. (c) Main stage, polymetallic lodes form in the

roof zone of the granite pluton by expulsion of magmatic fluids. (d) Meteoric waters circulate through the

granite as the system cools. Cu-Zn sulphides are deposited in a series of lodes (re-drawn after Smedley et al.,

1989)


(A1.2.1) 16 / 44

4.1 Summary

Fluids associated with both Sn-W greisen and Sn-Cu polymetallic lode mineralisation in South West England

are primarily of magmatic origin, In contrast fluids associated with post-granite crosscourse mineralisation

are distinctly non-magmatic and derived from sedimentary basins, possibly with a local meteoric water

component. Saline mine waters (known to extend to depths of at least 820 metres) are considered to be

palaeobrines that have been diluted by local meteoric water. These mine waters exploit N-S-trending

crosscourse structures in the granite and killas. Active fluid flow and mixing has, and continues to, play an

important role in the formation of the Cornubian Orefield.


Mineralising fluids, saline mine waters and shallow ground waters are reasonably well characterised

(e.g. by fluid inclusion, stable isotope, geochemical studies etc).

Significant amounts of data have been generated as part of the HDR programme (e.g. water

chemistry, stable isotopes, and fluid inclusions).

Fluid circulation is reasonably well understood in the shallow subsurface.

4.3 Limitations in our current understanding of fluids in South West England:

Much of the primary data that exists is related to the shallow sub-surface (<1,000 m, and often <200

m). Hence little is known about fluids existing at depths below 1,000 m, both in terms of chemistry

and circulation.

Mine water data are largely restricted to sites concentrated around the Carnmenellis granite.


(A1.2.1) 17 / 44

5 Mineralisation

The Cornubian Orefield has a complex, protracted (c. 100 Ma), multi-stage history of polymetallic

mineralisation. Mineralisation comprises a variety of styles, ranging from Devono-Carboniferous syngenetic

mineralisation, to recent placer and kaolin deposits. Although historically the south-west region was major

metal producer, the Drakelands Sn-W deposit (operated by Wolf Minerals Ltd) is the only active metal mine

in South West England. It is hosted within and around a dyke-like body of porphyritic granite, known as the

Hemerdon Granite that forms a cupola to the south-west of the main body of the Dartmoor Granite. The

deposit is one of the world’s largest tungsten deposits containing 35.7 million tonnes at a grade of 0.18%

WO3 and 0.03% Sn (Wolf Minerals, 2015). The Drakelands operation has a production capacity of more than

3,000 tonnes of tungsten concentrate per annum (Wolf Minerals, 2015). There is a long history of

mineralisation-related research in South West England, with a particular focus on granite-related

hydrothermal tin and tungsten-bearing deposits.

5.1 Historical production

Historically, the south-west region was a major metal producer. Mineral deposits in the region were

predominantly exploited for tin, tungsten, arsenic, zinc, lead and copper (Dines, 1956; Shail et al., 2014; Burt

et al., 2015). Approximate quantities of metal production in South West England are shown in Table 3.

Mineral or metal (Tons)

Sn metal 2,770,000

Cu metal 2,000,000

Fe ore 2,000,000

Pb metal 250,000

As (as As2O3) 250,000

Pyrite 150,000

Mn ores 100,000

Zn metal 70,000

W (as WO3) 5,600

U ore 2,000

Ag ore 2,000

Ag metal (from sulphide ore) 250

Co-Ni-Bi ores 500

Sb ores 300

Mo metal Minor

Au metal Minor

Barite 500,000

Fluorite 10,000

Ochre/umber 20,000

Kaolinite (china clay) 150,000,000

Table 3. Estimated total mineral and metal production from South West England. After Dines (1956),

Alderton (1993) and South Crofty PLC (1988-1998). Adapted from LeBoutillier (2002)


(A1.2.1) 18 / 44

5.2 Mineralisation in South West England

Four main stages of mineralisation have been identified in South West England, forming over about a 100

Ma period between the early Permian and the late Triassic. The mineralisation can be broadly divided on the

basis of its timing relative to granite emplacement as:

(1) Pre-granite orebodies of the sedimentary-exhalative type and shear-zone hosted Au-Sb mineralisation;

(2) Granite-related mineralisation, comprising greisens and sheeted vein complexes and polymetallic

sulphide lodes and;

(3) Post-granite mineralised Zn-Pb-Ag crosscourses (highlighted in Table 4). Figure 4 provides an overview of

the fluid chemistry of these mineralisation syles.

Pre-granite mineralisation comprises: (1) stratiform mineralisation that contains sub-economic enrichments

in base metals (Scrivener et al., 1989; Scrivener, 2006); and (2) metamorphogenic quartz-carbonate veins

that typically contain Sb-As-(Au) (Clayton et al., 1990). The main commodities associated with the early

stratiform mineralisation are iron and base metals. Orogenic shear-hosted Au-Sb-Ag mineralisation is limited

to basinal argillaceous lithologies with significant volumes of basic volcanic rocks. It is also spatially

associated with NNW-trending shear zones (Stanley et al., 1990). Fluid chemistry and structural data

indicates that the quartz-Au-Sb veins were precipitated early from CO2-rich metamorphic fluids with fluid

inclusion homogenisation temperatures (Th) in the range 315–280°C (Clayton et al., 1990).

Granite-related mineralisation formed largely during the early to mid-Permian. These mineral deposits were

historically of the greatest economic importance and were exploited for tin, tungsten, arsenic and base

metals. Granite-related mineralisation includes skarns and pegmatites, greisens and sheeted vein deposits,

and the main-stage polymetallic deposits. Localised skarn deposits have resulted from the thermal alteration

of calc-silicate minerals that have been altered by boron-rich fluids (Scrivener 2006). Volumetrically these

skarns are insignificant, thus reflecting the lack of carbonate-rich rocks in the region.

Greisen occurrences are restricted in extent, but common immediately adjacent to all plutons, including the

Isles of Scilly Granite (Grant and Smith, 2012; Sullivan et al., 2013; Shail et al., 2014). Greisen wall rock

alteration is characterised by the development of secondary mica around sheeted veins and in stockworks. It

occurs in the granite (endogranite) and the surrounding host rocks (exogranite). Endogranitic greisens occur

at St. Michaels Mount (Floyd et al., 1993), Cligga Head (Hall 1971; Jackson and Moore 1977), and Hemerdon

(Beer and Scrivener, 1982), while exogranitic greisens occur in the Tregonning and St Austell granites

(Dominy et al., 1995). The greisens comprise closely spaced quartz-tourmaline veins up to 0.1 m wide that

host wolframite, cassiterite, stannite, arsenopyrite and other sulphides. Fluid inclusions indicate that the

greisen-bordered veins were precipitated over a wide range of temperatures (Figure 4). Greisens represent

the earliest occurrence of significant fracture controlled magmatic-hydrothermal mineralisation in South

West England (Shail et al., 2014). Greisen bordered, sheeted veins and quartz‐(feldspar)‐wolframite lodes

formed within 2–3 Ma of granite emplacement, and overlap with muscovite cooling ages for the

host/adjacent pluton (Chen et al., 1993; Chesley et al., 1993).


(A1.2.1) 19 / 44

Table 4. Summary of mineralisation styles in the South West England (Cornubian) orefield (adapted from Andersen et al. 2016).

Pre-granite mineralisation Main ore minerals

1) Rifting and passive margin development (early Devonian- Carboniferous)

sedimentary-exhalative (SedEx) mineralisation Haematite Siderite Galena Sphalerite

2) Variscan convergence and continental collision (late Devonian-

Carboniferous) shear zone hosted Au-Sb + base metal mineralisation Gold Bournonite Sphalerite Chalcopyrite Tetrahedrite

Granite-related mineralisation

3) Early post-Variscan extension and magmatism (early Permian)

a) Magnetite-silicate skarns developed in metabasaltic hosts Magnetite Cassiterite

b) Sulphide-silicate skarns developed in calc-silicate granite hosts Cassiterite Arsenopyrite Pyrite Chalcopyrite Pyrrhotite

c) Greisen-bordered sheeted vein complexes Wolframite Cassiterite Chalcopyrite Sphalerite Bismuthinite

d) Quartz-tourmaline veins and breccias Cassiterite Haematite

e) Polymetallic sulphide lodes Cassiterite Chalcopyrite Wolframite Arsenopyrite Sphalerite

Post-granite mineralisation

4) Episodic intraplate rifting and inversion (late Permian – Cenozoic)

a) Crosscourse Pb-Zn ± F, Ba mineralisation Galena Sphalerite Arsenopyrite Chalcopyrite


(A1.2.1) 20 / 44

Polymetallic lodes containing cassiterite and chalcopyrite, and subordinate arsenopyrite, sphalerite, galena

and localised wolframite post-date the greisen bordered, sheeted veins. These lodes were historically the

main source of tin and copper in the region. The complex structure and mineralogy of these deposits, and

their strong spatial association with granite bodies, reflect the protracted magmatic-hydrothermal activity

associated with their formation (Scrivener 2006). These polymetallic lodes are generally orientated E-W and

developed between 269–259 Ma, although there is a suggestion that this reflects the dating of more than

one paragenetic episode (Chen et al., 1993; Clark et al., 1993). These lodes mark the final contribution of

magmatic-hydrothermal fluids to mineralisation in South West England (Shail et al., 2014).

Figure 4. Overview of the evolution of mineralising fluids in South West England (after Leveridge et al., 1990)

Post-granite mineralisation formed by east-west extension during regional extension-driven subsidence in

the Permian, which resulted in the formation of north-south-trending fracture systems. Subsequent

fracture‐controlled ingress of metal-complexing basinal fluids from Permo‐Triassic sedimentary successions

into the Variscan basement resulted in the stripping of metals from metalliferous source rocks, and the

formation of what is known as ‘crosscourse’ mineralisation (Scrivener et al., 1994). This comprises

polymetallic veins dominated by lead, zinc and copper, which locally host antimony-bearing minerals. The

north-south-trending crosscourse mineralisation postdates the granite related Sn-W-Cu mineralisation by


(A1.2.1) 21 / 44

30–40 Ma (Scrivener et al., 1994). The crosscourse veins were primarily exploited for lead, zinc, silver,

fluorite and baryte, typically within Devonian and Carboniferous successions.

In addition to the styles of mineralisation described above, there are a number of less significant types of

mineralisation that are not described in this report. These include: syn-granite tourmaline-tin veins

(Scrivener 1982; Bromley 1989); tourmaline breccias (London et al., 1995; Müller and Halls 2005); post-

granite, low temperature manganese and iron replacement deposits; and gold-carbonate veins (Jackson et

al., 1989). Following granite emplacement, descending meteoric water resulted in alteration of feldspar,

leading to high levels of kaolinisation in the St Austell and Dartmoor granites. This has not been discussed in

this report as it is not metallic mineralisation. However, the following references provide a good overview of

this late-stage alteration: Sheppard (1977), Bray and Spooner (1983) and Bristow and Exley (1994).

5.3 Summary

The south-west of England is a historically important mining region and has produced a significant range and

volume of metals. However, the region is best known for its tin and copper production. Mineralisation in

South West England can be categorised into four broad styles that have been related to the timing of granite

emplacement (i.e. pre-granite, granite-related, and post-granite). The most significant mineralisation in

South West England from an economic perspective is related to magmatic-hydrothermal activity associated

with granite emplacement. Importantly a significant, and growing, body of research and data exists on

mineralisation in South West England.


A large amount of data (e.g. geochronology, fluid composition, mineralogy, geochemistry, etc.) has

been generated from ore deposit research in South West England.

A good understanding is developing of how magmatism, fluids and large-scale structures have

interacted to produce economic mineralisation. This data and knowledge has implications for

engineered geothermal systems.

5.5 Limitations in our current understanding of the mineralisation in South West England:

There is significant uncertainty about the form and scale of mineralisation below 1,000 m.

The distribution of data coverage is generally skewed towards areas where economic mineralisation

has been exploited or commercial mineral exploration has occurred.


(A1.2.1) 22 / 44

6 Structure and stress-field measurements

South West England is a structurally complex region whose geological past has been dominated by Variscan

tectonics. British Geological Survey mapping, academic research and seismic surveys have led to the

identification of three main deformational phases associated with Variscan orogenesis. Two phases are

related to crustal shortening (D1 and D2) whilst the third (D3) is associated with crustal extension during

orogenic collapse (Alexander and Shail, 1996; Leveridge et al., 2002). The D1 deformation event (c. 385 Ma) is

characterised by: (1) large-scale (10s km), NW-SE-trending strike-slip faults; (2) a NNW-trending mineral

lineation; and (3) E-W-trending folds. Structures associated with the second deformation event (D2) are

similar to those formed during D1, but D2 structures are generally more steeply dipping. The D3 event (c.

305–300 Ma) occurred in response to orogenic collapse and associated crustal extension. It resulted in the

development of steep to gently inclined WNW-ESE-trending extensional faults (Alexander and Shail, 1996;

Leveridge et al., 2002). Regionally extensive NNW-SSE-trending crosscourse structures formed during the

Permian in response to a period of crustal extension (Scrivener et al., 1994; Shail and Alexander, 1997).

Figure 5. Map of the distribution of major NW-SE-trending faults and granite bodies in South West England

(drawn from BGS mapping data)

In South West England both granite and the killas have inherently poor permeability (Heath et al., 1985).

Accordingly, fluid circulation in the region is largely controlled by regional-scale structures (e.g. NW-SE-

trending faults) (Figure 5) and fractures (Heath et al., 1985; Bromley et al., 1989; Smedley et al., 1989).

Fractures in the granite are primarily the result of magma chamber processes, for example cooling and

hydro-fracturing (caused by the movement of magmatic fluids). In contrast fractures in the killas are

principally the result of granite emplacement. Local zones of high-fracture density, in both granite and killas,


(A1.2.1) 23 / 44

may also be associated with episodes of late faulting. However, the permeability and connectivity of these

fractures, particularly at depth, remains enigmatic (Heath et al., 1985).

Figure 6. Principal stress orientation and magnitude in the Carnmenellis granite as determined by in-situ

hydraulic fracture tests at the Rosemanowes HDR test site (re-drawn from Pine and Batchelor, 1984)

A relatively small number of stress field measurements were made on the Carnmenellis granite, during the

1980s. Both hydraulic fracture tests and overcoring tests were conducted at the Rosemanowes HDR test site

at depths of 0–2,000 m and 800 m, respectively. All of the tests were successful in achieving ‘breakdowns’

(i.e. the point at which the fluid pressure is high enough to fracture the rock), in only one of the tests was the

hydraulic fracture fully characterised using microseismic monitoring. A series of overcoring tests were also

conducted in the South Crofty mine (on the edge of the Carnmenellis granite) at a maximum depth of 790 m.

A similar, but unrelated, set of stress field tests (i.e. hydraulic fracturing and overcoring) were carried out at

Carwynnen quarry, also on the Carnmenellis granite. Although the hydraulic fracture tests and overcoring

were conducted at much shallower levels, 700 m and 34 m, respectively the two studies confirmed the

presence of two joint sets in the Carnmenellis granite: one trending NNW-SSE-trending and the other ENE-

WSW. The results from both studies show that the in-situ stress orientation is about 30° off parallel from


(A1.2.1) 24 / 44

that of the natural joint sets observed in the granite. The studies also demonstrated that maximum in-situ

stress (σH) is approximately 70 MPa in the NNW-SSE direction, whilst the minimum in-situ stress (σh) is about

30 MPa in the ENE-WSW direction (Figure 6). It was found that stress magnitude and orientation at depth

are relatively consistent across the Carnmenellis granite, and are fairly consistent with measurements from

the rest of the United Kingdom. Importantly it was found that shearing along these natural joints was more

likely than dilation, unless very high injection pressures were used (Pine and Batchelor, 1984; Evans, 1987;

Cooling et al., 1988; Haimson et al. 1989; Turnbridge et al., 1989).

6.1 Summary

The south-west of England is a structurally complex region whose geological past has been dominated by

Variscan tectonics, which resulted in at least three episodes of deformation. The permeability of rocks (i.e.

granites and metasedimentary rocks) in South West England is inherently very low, and as such faults and

fractures are locally and regionally important in terms of fluid flow. In particular the presence of large-scale,

NNW-SSE-trending crosscourse structures are an important consideration for the design of any EGS system

in South West England. However, the permeability and connectivity of these features, particularly at depth,

remains enigmatic. Assessment of the stress field in South West England shows it is comparable to other

parts of the UK. Two joint sets occur in the Carnmenellis granite and analysis has determined the relative in-

situ stress orientation and the maximum and minimum in-situ stress values.

6.2 How South West England can positively contribute to the aims of the aims of CHPM2030:

In-situ stress measurements have been made at depth (up to 2,000 m) in South West England.

Relative to many other onshore parts of the UK the stress field in South West England is fairly well

constrained.

Consistency in the approach used for making in-situ stress field measurements in South West

England means the results of different survey are directly comparable.

6.3 Limitations in our current understanding of the stress field in South West England:

Whilst existing data provide a good indication of the stress field in the upper 2 km of crust in South

West England, uncertainty about the type of lithologies which occur at greater depth and their

structural characteristics means the validity of extrapolating these measurements to the target

depths of an EGS system is a consideration.

Only a small number of deep (specific ~2,000m) stress measurements are available for South West

England. This is a particular issue given that significant heterogeneity in stress orientation and

magnitude may exist.


(A1.2.1) 25 / 44

7 Deep sub-surface temperatures in South West England

7.1 United Kingdom overview

Between 1977 and 1994 the UK government funded an assessment of potential geothermal energy

resources. This programme considered three main elements: (1) appraisal of heat flow; (2) potential of hot-

brines from deep hyper-saline aquifers (HAS) for direct heat production; and (3) the potential of EGS, which

included the HDR Programme. A catalogue of sub-surface temperatures, heat flow estimations, thermal

conductivity measurements and geochemical data was compiled by BGS (Burley and Edmunds, 1978). It was

subsequently updated by Burley and Gale (1982), Burley et al. (1984) and Rollin (1987). The findings of this

work were summarised by Downing and Gray (1986a, 1986b), BGS (1988), Parker (1989, 1999) and most

recently in Barker et al. (2000).

A heat flow map (Figure 7) of the UK was generated and subsequently revised (Downing and Gray, 1986a, b;

Lee et al., 1987; Rollin, 1995; Rollin et al., 1995; and Barker et al., 2000). The map shows two areas of

enhanced heat flow that are associated with the radiogenic granites of South West England (Cornwall) and

the buried granites of northern England. Temperatures at 5 km depth were estimated to be as high as 180–

190°C in Cornwall, and up to 130–170°C in northern England, but rarely exceeded 95°C elsewhere. The

average geothermal gradient is 26°C km1 but locally it can exceed ≈ 35°C Km-1 (Busby, 2010). The average UK

heat flow is approximately 55 mWm-2.

Figure 7. Heat flow map of the UK (after Busby, 2010)


(A1.2.1) 26 / 44

7.2 South West England overview

Figure 8. Revised estimated granite-related average temperatures (°C) at a depth of 5 km and the percentage

increases (in brackets) over previously published estimates. Locations of five towns, are shown in blue; PEN =

Penzance; StI = St Ives; CAM = Camborne; RED = Redruth and; StA = St. Austell (after Busby and Beamish,

2016)

Of specific interest to this project are the data for the south-west region of the UK, in particular Cornwall

where the geothermal gradient is estimated to be highest. Barker et al. (2000) noted that the average heat

flow in the Cornubian granites of South West England is ≈ 120 mWm-2. Heat production values for the

Cornubian granites can be found in Wheildon et al. (1981) and Thomas-Betts et al. (1989). Beamish and

Busby (2016) have re-assessed the quality of these original data sets, and in addition have recalculated the

heat flows in accordance with our improved understanding of paleoclimate. This has resulted in revised

values that are higher than the original estimates, with the consequence that temperatures at depth are also

greater i.e. at 5 km they range from ≈ 185°C for the Dartmoor granite to ≈ 220°C for the St Austell granite,

(Figure 8) which is an increase of between 6 and 11 per cent. The vast majority of the temperature data

comes from shallow wells (about 100 m), with additional data available from some former mines e.g. Geevor

mine at about 400 m and South Crofty at about 600 m. As such, these estimated temperatures are based on

a model that assumes constant heat production to a depth of 5 km. There are only very limited (historic)

temperature data available from depths below 600 m, largely comprising data from the former HDR Project

at Rosemanowes Quarry, near Redruth, on the Carnmenellis granite. Here three deep wells were drilled, the

deepest being a 2,600 m vertical well, plus several shallow boreholes (300 m). Barker et al. (2000) reported

that measured temperatures were ≈ 80°C at 2,100 m depth (in well RH12) and ≈ 100°C at 2,600 m (in well


(A1.2.1) 27 / 44

RH15). The revised heat flow data from Beamish and Busby (2016) gives slightly higher, estimated,

subsurface temperatures of ≈ 84°C, and ≈ 102°C at 2,100 m and 2,600 m, respectively. Unfortunately, UK

government funding was withdrawn from the HDR project before it could investigate conditions at 5–6 km,

and it closed in 1994. Although its three deep wells are still accessible, it is unclear if any temperature

measurements have been obtained since the close of the project. To date no other deep wells have been

drilled in the region.

7.3 Summary

A significant body of data exists from a British government funded assessment of the potential geothermal

energy resources in the UK, over a period spanning three decades. South West England, specifically Cornwall,

was estimated to have the highest geothermal gradient in the UK. Temperatures at 5 km depth in the

Cornubian granites are estimated to be in the range of ≈ 185°C–220°C. However, it is important to note that

these estimates are based on modelled heat flow and heat production. Data from depths of >600 m is very

limited, but the measured temperature from one of three deep wells in the Carnmenellis granite was ≈

100°C at 2,600 m. It is notable that these three well are still accessible.


A significant dataset exists from investigation of the geothermal potential of the UK. However, some

of this data may be only available in analogue format.

Three deep boreholes are still accessible within the Carnmenellis granite, meaning there is potential

for new measurements to be taken to validate existing data and new models and estimates.

7.5 Limitation in our current understanding of deep sub-surface temperatures in South West

England:

Despite a significant body of data there is still significant uncertainty about the temperatures that

might exist at the depth of an EGS system as most estimates and models are based on extrapolation

of near surface historical data.

Selected historical data is only available in analogue format.

The HDR project ceased in 1994, with little associated work taking place during the subsequent 22

years.


(A1.2.1) 28 / 44

8 Hot Dry Rock (HDR) research programme

Figure 9. Location of the Rosemanowes HDR test site in relation to the Carnmenellis granite outcrop (re-

drawn from Edmunds et al., 1989)

In 1984, a programme of work, funded by the UK Department of Energy (DEn) and the Commission of the

European Communities (CEC), was undertaken by the British Geological Survey (BGS) to assess the UK for its

geothermal potential. Over the same time period (1977–1984) the Camborne School of Mines (CSM) was

assessing the feasibility of creating HDR geothermal systems at a test site at the Rosemanowes quarry, on

the Carnmenellis granite, in Cornwall. The assumption was made that the behaviour and characteristics of a

HDR system could be modelled using geochemistry, geophysics, and physical properties. Between 1985 and


(A1.2.1) 29 / 44

1989 the Department of Energy and the Commission of the European Communities funded a detailed

geochemical investigation of the HDR site at Rosemanowes. These investigations were undertaken by the

BGS, the then NERC Isotope Geology Centre (NIGC), the University of Bath (UoB) and CSM. In 1987 an

informal working group (the UK Hot Dry Rock Geochemistry Group) was established to align the geochemical

programme more closely with the physical properties and geophysical work being undertaken by CSM at the

Rosemanowes test site. The BGS output from this work was series of seven volumes (Edmunds et al. 1989;

Richards et al. 1989; Andrews et al. 1989; Smedley et al. 1989; Bromley et al. 1989; Savage et al. 1989 and;

Richards et al. 1989) that outline the methods and results of geochemical HDR research at the Rosemanowes

test site (Edmunds et al., 1989) (Figure 9). Similar outputs (authored by CSM) that describe the physical

properties of the HDR system are not held by the BGS.

An overview of the aims and main conclusions of each volume is given below along with a schematic of the

HDR system at the Rosemanowes test site (Figure 10). Volumes 1 and 2 (Edmunds et al. 1989; Richards et al.

1989) are not described here as they are primarily, overview-type documents (Volume 1 provides a synopsis

of the other 6 volumes, whilst Volume 2 provides an overview of geochemical results collected as part of the

HDR programme). Full details of methods used and results obtained are given in each of the volumes.

Figure 10. A schematic diagram showing the configuration of the 2 and 2.5 km test wells at

the Rosemanowes HDR test site (re-drawn from Edmunds et al., 1989)


(A1.2.1) 30 / 44

8.1 Volume 3: The use of natural radioelement and radiogenic noble gas dissolution for modelling

the surface area and fracture width of a Hot Dry Rock system (Andrews et al. 1989)

Scope of the report

The movement of natural radioelements (e.g. 226Ra) and radiogenic noble gases (e.g. 222Rn) in the HDR

system was investigated to: (1) characterise changes in reservoir surface area; (2) develop a routine

monitoring method for determining 222Rn in the HDR return fluids; (3) determine the effect of surface

mineralisation and physical conditions on 222Rn flux, and hence upon derived reservoir parameters; (4)

estimate the effect of fracture width variation on the radon model; and (5) assess geochemical changes in

radioelement chemistry induced by HDR circulation.

Conclusions

Reservoir surface area showed a general increase as flow tests progressed.

Tracer transit times of up to 400 hours were observed within fractures.

Mineralised surfaces, particularly those hosting uranium-rich minerals, dramatically increase the 222Rn flux of the system.

Uranium mobilisation occurs in the system in response to fluid circulation.

8.2 Volume 4: Fluid circulation in the Carnmenellis granite: hydrogeological, hydrogeochemical,

and palaeofluid evidence (Smedley et al. 1989)

Scope of the report

Investigation of the hydrogeology and hydrogeochemistry of the Carnmenellis granite helped to explain

important processes, such as: (1) granite-water interaction; (2) fluid-flow in granite; and (3) solution-

precipitation reactions. Understanding natural fluid flow can be useful to HDR development as it provides an

analogue to artificial short-term circulation in the HDR reservoir.

Conclusions

Groundwater flow in both granite and killas is dominated by fracture permeability; primary

permeability in both rock types is low. In particular it is the north-south-tending crosscourse

structures that are the most important water-conducting fractures.

Shallow groundwater compositions show a strong affinity with the local geology and soils. In many

cases the element concentrations are very lithology-specific, for example Cl, HCO3, pH, Na, Ca, Mg

levels are highest over the killas, whilst Al, Ba and Rb levels are higher over the granite.

Saline thermal waters discharging in deep mines (depths down to 820 m) are effectively dilute

palaeobrines (formed by long-term water-rock interaction) that have mixed with circulating local

meteoric waters.

8.3 Volume 5: Mineralogy and geochemistry of the Carnmenellis granite (Bromley et al. 1989)

Aims of the report

In order to fully understand the geological constraints on HDR reservoir development the geology of the

region is considered in detail. In particular the following areas of enquiry are of interest: (1) the spatial

variation in the petrological and geochemical characteristics of the granites ; (2) the spatial variation in the

nature of the fracture system ,and the character of fracture mineralogy and adjacent wall-rock alteration; (3)


(A1.2.1) 31 / 44

the mechanisms and products of natural fluid-rock interaction under conditions similar to those pertaining in

an artificial reservoir, and which might provide useful analogues for reservoir behaviour; and (4) the

prediction of geological conditions at depths of 5–7 km in regions where commercial reservoirs may be

developed.

Conclusions

Rock at depth is likely to be an inhomogeneous mixture of vuggy, pegmatitic granite and magmatic

residues (i.e. restite). Thus water-rock interaction would be significantly different from that

predicted by experiments on samples of ‘average’ Cornubian granite.

The ability to drill an inhomogeneous mixture of granite and restite is likely to be very different from

that of standard granite alone.

Localised zones of argillic alteration, associated with crosscourse structures at depth, may hamper

drilling operations.

North-south-trending crosscourse structures are likely to extend to significant depths and as such

represent important zones of increased permeability. However, they may also lead to extensive fluid

loss from the HDR system.

8.4 Volume 6: Experimental investigation of granite-water interaction (Savage et al. 1989)

Scope of the report

Investigation of chemical reactions that take place between circulating fluids and reservoir rock in a HDR

system is important because: (1) it provides an indication of the evolution of the physical characteristics of a

reservoir under development (e.g. temperature), and (2) it provides information about the potential lifetime

of a reservoir undergoing commercial operation. Laboratory experiments were undertaken to evaluate the

magnitude and rate of water-rock reactions, including: (1) the surface-area dependant release rate of a

variety of chemical component from the Carnmenellis granite under likely in-situ conditions at EGS depths;

and (2) the investigation of the chemical reaction of Carnmenellis granite with possible circulation fluids.

Conclusions

The concentration (by weight) of elements in the output fluid from laboratory experiments was as

follows (from highest to lowest): SiO2 > Ca > Na > K > Fe > Mn > Rb > Li > Cs > Sr.

The relative molar release rates of the elements (from highest to lowest) was: SiO2 > Na > Ca > K > Fe

> Mn > Li > Rb > Sr > Cs.

Changes in pH were only found to affect Al (increased with increasing pH), SiO2 (increased with

increasing pH) and Fe (decreased with increasing pH).

Use of dilute surface water as an EGS ‘top-up’ fluid was superior to using seawater, the latter causing

potential problematical precipitation of hydrated magnesium sulphate phases.

Bulk granite dissolution rates vary significantly from 6 x 10-10 g m-2 s-1 (expressed as SiO2 release) at

60°C to 5 x 10-7 g m-2 s-1 (expressed as Ca release) at 100°C.

Individual mineral dissolution rates also vary significantly. Experiments at 80°C have generated the

following estimated rates of dissolution: 2 x 10-11 – 8 x 10-10 mol m-2 s-1 (biotite); 4 x 10-11 – 2 x 10-10

mol m-2 s-1 (oligoclase); 2 x 10-10 – 4 x 10-10 mol m-2 s-1 (labradorite) and; 1 x 10-15 – 2 x 10-14 mol m-2

s-1 (tourmaline).


(A1.2.1) 32 / 44

8.5 Volume 7: Geochemical prognosis for a Hot Dry Rock system in South West England (Richards

et al. 1989)

Aims of the report

The geochemical aspects of the design and operation of a commercial HDR geothermal system in granite, in

South West England are reviewed and modelled in order to predict: (1) the composition of the circulation

fluid; (2) the potential for chemical problems associated with the wells and surface plant (including

effluents); (3) the rates of water-rock reactions in the HDR reservoir, and how this might affect hydraulic

performance; and (4) the potential use of geochemistry in characterising the performance of the HDR

reservoir during and after its creation.

Conclusions

The most appropriate circulation fluid is predicted to be a mildly-saline, neutral to mildly-alkaline

local surface water, with low to moderate total sulphur (20–150 ppm SO4) and low to moderate total

sulphide (5–10 ppm H2S).

Silica and/or carbonate-based scaling are likely to the biggest issue for wells and surface plant.

Predicted arsenic (c. 1 ppm), boron (c. 1 ppm), fluoride (c. 10–20 ppm) and silica (c. 300 ppm)

concentrations in the circulation fluid mean they could not be discharged straight into the

environment without prior treatment.

Mineral dissolution is likely to result in widening of fractures (by up to 1 mm over a 25-year lifetime)

and thus will have an impact on reservoir hydraulics.

However, the precipitation of secondary minerals (e.g. zeolites, clays and calcite) as a result of

granite-water reactions would also have a potentially negative impact on porosity and reservoir

hydraulics.

8.6 Summary

The UK HDR geochemistry group was a collaboration between BGS and CSM; it sought to use geochemistry

to characterise the behaviour and performance of an engineered geothermal system (EGS). A number of

important conclusions were drawn from this work, including: fluid residence time, mineral dissolution rates,

surface area modelling, and potential problems related to chemistry (e.g. scaling of surface plant and

‘clogging’ of the reservoir by the development of secondary minerals).


Data associated with the HDR programme is specific to engineered geothermal systems.

Samples, data and observations gathered as part of the HDR project are derived from boreholes

down to about 2.6 km deep. This is currently much deeper than similar boreholes in the UK, and thus

provides a useful insight into the deep geothermal environment in South West England.

8.8 Limitation in our current understanding of South West England:

Data and interpretation are specific to the Carnmenellis granite.

Only a small amount of core material from the original HDR programme is available.

Significant uncertainty remains in terms of actual conditions that might be encountered in a deep (c.

4–6 km) commercial HDR system (i.e. many of the conclusions are based on predictive models).

Much of the data are only available in analogue format.


(A1.2.1) 33 / 44

9 Data holdings at BGS

The BGS is the world’s longest established national geological survey, and is the UK's premier provider of

objective and authoritative geoscientific data. It has been gathering geoscience data and information about

the subsurface in the UK and other countries for more than 180 years. It is a data-rich organisation with

more than 500 datasets in its care, including environmental monitoring data, digital databases, physical

collections (e.g. borehole core, rocks and minerals), records and archives. Importantly, a great many of these

datasets are openly available, many of which provide complete, seamless UK coverage at a number of scales.

Certain other datasets may be subject to confidentiality clauses and/or licencing fees. Information about

how to access these datasets can be found here: http://www.bgs.ac.uk/data/home.html?src=topNav.

These national datasets are available to the CHPM2030 project, and can provide a very useful starting point

to assess CHPM potential in South West England. Many of the datasets cover much of the UK, whereas

others are specific to South West England (e.g. geophysical data conducted as part of the TELLUS project

(http://www.tellusgb.ac.uk/). Most of the data stored relate to surface exposures or the near-surface

environment. Although, the datasets do contain much information about a large number of boreholes and

mines, most does not extend below 100 m, and there is limited data below 1,000 m. This places significant

constraints on predictions when extrapolating the data to EGS depths (i.e. 4–6 km). The datasets are also of

differing ages and levels of detail - reflecting changing national priorities over the past decades. In terms of

geothermal development, much of the data are derived from a national programme of work in the 1980s

and early 1990s. As a consequence, the data reflect monitoring technology and ideas at that time, and much

of the data are in analogue format.

9.1 Summary

The BGS maintains a large number of datasets (over 500) that include environmental monitoring data, digital

databases and physical collections (i.e. borehole core and rock samples). Many of the datasets offer

complete, seamless coverage of the UK at a variety of scales. A good number of these datasets are also freely

and openly available.


The BGS holds a large amount of information about the geological, geophysical and geochemical

properties of the UK.

Data coverage for the south-west region is very good.

9.3 Limitations in our current understanding of South West England:

The majority of the data sets only relate to the shallow sub-surface 0–1,000 m).

Some datasets are incomplete (e.g. rock stress data are restricted in spatial coverage).

Some datasets are based on old data that have been digitised.

http://www.bgs.ac.uk/data/home.html?src=topNav


(A1.2.1) 34 / 44

Table 5. Summary of datasets pertinent to CHPM2030 held by the BGS (continued on next page)

Datasets Description Scale Coverage Access cost Link

Hydrogeology

Depth to

groundwater

Spatial model showing depth (m) to

the phreatic water table. 1:50,000 Great Britain 15p per km2

http://www.bgs.ac.uk/products/hydroge

ology/depthToGroundwater.html

Hydrogeological

maps

Spatial model of aquifer potential

based on geological formations. 1:625,000 UK Free

http://www.bgs.ac.uk/products/hydroge

ology/maps.html

Permeability

Spatial model showing flow regimes

(e.g. fracture flow) and relative flow

rates.

1:50,000 Great Britain 10p per km2 http://www.bgs.ac.uk/products/hydroge

ology/permeability.html

Geophysics and remote sensing

LiDAR

High-resolution LiDAR digital terrain

model (DTM) and digital surface

model (DSM).

Resolution

information

on website

SW England Free http://www.tellusgb.ac.uk/data/home.h

tml

Airborne

magnetics

Airborne survey data showing

variation in the magnetic field.

Resolution

information

on website

SW England Free http://www.tellusgb.ac.uk/data/airborn

eGeophysicalSurvey.html

Airborne

radiometrics

Airborne survey data for the

radioactive isotopes Th, U, and K.

Resolution

information

on website

SW England Free http://www.tellusgb.ac.uk/data/airborn

eGeophysicalSurvey.html

Land gravity A database of over 165,000 gravity

observations. N.A. Great Britain Free

http://www.bgs.ac.uk/products/geophys

ics/landGravity.html

Geophysical

borehole logs

An archive of geophysical downhole

log data. N.A. Various £30 per hole

http://www.bgs.ac.uk/products/geophys

ics/boreholeLogs.html

http://www.bgs.ac.uk/products/hydrogeology/depthToGroundwater.html

http://www.bgs.ac.uk/products/hydrogeology/depthToGroundwater.html

http://www.bgs.ac.uk/products/hydrogeology/maps.html

http://www.bgs.ac.uk/products/hydrogeology/maps.html

http://www.bgs.ac.uk/products/hydrogeology/permeability.html

http://www.bgs.ac.uk/products/hydrogeology/permeability.html

http://www.tellusgb.ac.uk/data/home.html

http://www.tellusgb.ac.uk/data/home.html

http://www.tellusgb.ac.uk/data/airborneGeophysicalSurvey.html




http://www.bgs.ac.uk/products/geophysics/landGravity.html

http://www.bgs.ac.uk/products/geophysics/landGravity.html

http://www.bgs.ac.uk/products/geophysics/boreholeLogs.html

http://www.bgs.ac.uk/products/geophysics/boreholeLogs.html


(A1.2.1) 35 / 44

Datasets Description Scale Coverage Access cost Link

Geology

UK3D A 3D bedrock model of the UK at 1:625,000 scale.

1:625,000 UK Free http://www.bgs.ac.uk/research/ukgeology/nationalGeologicalModel/gb3d.html

Geological maps 2D lithological and structural mapping (bedrock and superficial).

*1:50,000 UK **20p per km2 http://www.bgs.ac.uk/products/digitalmaps/DiGMapGB_50.html

Boreholes

Borehole database

A database of over one million records of boreholes, shafts and wells.

N.A. Great Britain Free http://www.bgs.ac.uk/products/onshore/SOBI.html

Borehole scans Online access to more than one million borehole logs.

N.A. Great Britain Free http://www.bgs.ac.uk/data/boreholescans/home.html

Physical properties

Rock stress Online access to almost 1,000 rock stress measurements.

N.A. Great Britain Free http://mapapps.bgs.ac.uk/rockstress/home.html

Discontinuities Spatial model of discontinuities in bedrock (e.g. fractures and faults).

1:50 000 Great Britain **30p per km2 http://www.bgs.ac.uk/products/groundConditions/discontinuities.html

Geochemistry

GBASE

south-west

Geochemical baseline survey of soils and stream sediments.

N.A. SW England Free http://www.bgs.ac.uk/products/geochemistry/GbaseSWproducts.html

Minerals

Britpits A database of over 180,000 records of active and inactive mine and quarry workings.

N.A. UK ***£50 per region

http://www.bgs.ac.uk/products/minerals/BRITPITS.html

Footnotes:

* Other scales available (e.g. 1:25,000; 1:10,000; 1:625,000).

** Commercial rate. Free to use via the BGS web-based viewer: http://mapapps.bgs.ac.uk/geologyofbritain/home.html

*** The full dataset comprises fifteen regions.

http://www.bgs.ac.uk/research/ukgeology/nationalGeologicalModel/gb3d.html

http://www.bgs.ac.uk/research/ukgeology/nationalGeologicalModel/gb3d.html

http://www.bgs.ac.uk/products/digitalmaps/DiGMapGB_50.html

http://www.bgs.ac.uk/products/digitalmaps/DiGMapGB_50.html

http://www.bgs.ac.uk/products/onshore/SOBI.html

http://www.bgs.ac.uk/products/onshore/SOBI.html

http://www.bgs.ac.uk/data/boreholescans/home.html

http://www.bgs.ac.uk/data/boreholescans/home.html

http://mapapps.bgs.ac.uk/rockstress/home.html

http://mapapps.bgs.ac.uk/rockstress/home.html

http://www.bgs.ac.uk/products/groundConditions/discontinuities.html

http://www.bgs.ac.uk/products/groundConditions/discontinuities.html

http://www.bgs.ac.uk/products/geochemistry/GbaseSWproducts.html

http://www.bgs.ac.uk/products/geochemistry/GbaseSWproducts.html



http://mapapps.bgs.ac.uk/geologyofbritain/home.html


(A1.2.1) 36 / 44

10 Conclusion

This report describes the breadth of information available for South West England, which is relevant to the

development of enhanced geothermal systems, except data held by CSM relating to physical properties

testing and geophysics at the HDR test site. South West England is a geologically complex region with a long

and significant history of metal mining, producing primarily tin and copper. The requirement to better

understand the economic mineral potential of the region has resulted in almost 200 years’ worth of applied

and academic research. These studies have generated a huge volume of data that includes: geological

mapping, geophysical and geochemical surveys, and numerous reports and peer-reviewed publications.

Another potentially important resource in South West England is geothermal energy. Previous geothermal

research in the region peaked between the 1970s and 1990s, and focussed largely on the high heat flows

associated with the Cornubian granites. In 1984 this programme of work was undertaken by the BGS to

assess the UK’s geothermal potential. Over the same time period (1977–1984) the Camborne School of

Mines (CSM) was assessing the feasibility of creating HDR geothermal systems at a test site at the

Rosemanowes quarry, on the Carnmenellis granite, in Cornwall.

In summary a huge amount is known about the geology, mineralisation, fluid history and geothermal

potential of South West England. A significant body of data underpins this knowledge base, the majority of

which is freely, or openly available. However, there are limitations. For example, much of this data, with the

exception of the HDR datasets, only relates to the upper 1,000 m of the crust. This has significant

implications regarding the accuracy of modelled conditions in an enhanced geothermal system (EGS) at

greater depths. There are also ‘gaps’ in the data (e.g. very limited deep-geophysical data), and some datasets

have not been updated since their creation several decades ago.


(A1.2.1) 37 / 44

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REPORT ON DATA AVAILABILITY:

PORTUGUESE IBERIAN PYRITE BELT

This project has received funding from the European Union’s Horizon 2020 research and innovation

programme under grant agreement no 654100.

Summary:

This report provides an overview of geoscientific data and information relating south-west

Iberian Pyrite Belt, Portugal, with a particular focus on its geology, structure, stress-field

characteristics, mineralisation and previous geothermal research in the region.

Authors:

Elsa Cristina Ramalho, geological engineer, João Xavier Matos, economic geologist, João

Gameira Carvalho, geophysicist (Laboratório Nacional de Energia e Geologia)


(A1.2.2) 2 / 38

Table of contents

1 Preface ...................................................................................................................................................... 5

2 Country specific issues .............................................................................................................................. 8

2.1 Climate ............................................................................................................................................... 8

2.2 Active mining exploration in IPB ........................................................................................................ 8

3 CHPM2030 Goals in the portuguese IPB sector ........................................................................................ 9

3.1 Properties to study (stratigraphic, lithological, structural, mineralogical, chemical) ......................... 9

3.2 Working progress considering project goals ...................................................................................... 9

4 Previous research and available data ...................................................................................................... 10

4.1 Structural settings inferred from geology and geophysics (incl. drilling) ......................................... 10

4.2 Geometry and composition of ore deposits .................................................................................... 11

4.3 Hydraulic properties, deep fluid flow ............................................................................................... 12

4.4 Fluid composition, brines, meteoric waters ..................................................................................... 12

4.5 Thermal properties and heat flow ................................................................................................... 13

4.6 Geophysical Exploration surveys in the IPB...................................................................................... 18

5 Identifying target sites for future CHPM ................................................................................................. 24

5.1 Extending existing models to greater depth, integrating data down to 7 km .................................. 24

5.2 Knowledge gaps and limitations ...................................................................................................... 25

6 Discussion and concluding remarks ........................................................................................................ 27

6.1 How the Iberian Pyrite Belt Neves Corvo sector can positively contribute to the aims of CHPM2030

28

7 Datasets pertinent to CHPM2030 held by LNEG ..................................................................................... 29

8 Acknowledgements ................................................................................................................................. 31

9 References .............................................................................................................................................. 31


(A1.2.2) 3 / 38

List of Figures

Figure 1. Location of the central area of the IPB Portuguese sector within the scope of the Iberian Peninsula

and main geological groups. Location of the IPB massive sulphide deposits and intense acid mine drainage

(Inverno et al., 2015, Abreu et al., 2010). Active mining: Neves Corvo (Somincor-Lundin Mining) and Aljustrel

(Almina). Scale (line): 5 km ................................................................................................................................. 5

Figure 2. Mineral deposits, their morphological type and dimension of Southern Portugal with special focus

to the IPB (delimited in purple) .......................................................................................................................... 6

Figure 3. Central area of the IPB Portuguese sector (ad. Matos and Filipe Eds., LNEG 2013): mineral

occurrences – circles: red – massive sulphides, dark purple – Mn, green – Cu, blue – Ba(Pb) and exploration

drill holes (triangles). Map grid: 1:25,000 scale maps (16 km x 10 km). ............................................................ 7

Figure 4. a) Average annual temperature (°C) and b) Average annual precipitation (mm) (source

http://www.ipma.pt). ........................................................................................................................................ 8

Figure 5. Neves Corvo general geological section, adapted from Relvas et al., 2006. Location of the lower

sector of the Corvo massive ore lens (blue arrow) .......................................................................................... 10

Figure 6. Neves Corvo massive sulphide ore, showing primary banded structures and rich layers of

chalcopyrite and sphalerite. Sample collected at 610 m depth ....................................................................... 11

Figure 7. Heat flow map for mainland Portugal (http://geoportal.lneg.pt) ...................................................... 13

Figure 8. Geothermal gradient for Mainland Portugal with the IPB sector (http://geoportal.lneg.pt) ............ 14

Figure 9. Heat Flow Density estimations (W/m2) for the IPB Portuguese sector. Geology ad. from

http://geoportal.lneg.pt ................................................................................................................................... 18

Figure 10. (left) Geological map 1:1K (http://geoportal.lneg.pt) (right) Magnetic Total Magnetic Field Intensity

map with reduction to pole, based on RTZ survey, ad. Represas et al. 2016 ................................................... 19

Figure 11. Gravimetric and magnetic data a) plotted over CRS stack for seismic profile 1 without b) and with

post-stack time migration with overlaid stratigraphic and structural interpretation c). The locations of drill-

holes CT01 and CT08001 are shown (blue line) and a geological cross-section based on these two drill-holes

and previously acquired seismic reflection data is overlaid the interpreted stacked section. Mfi: Magnetic

field intensity (reduced to the pole); Ba: Bouguer anomaly. Black lines: faults; Yellow lines/T: thrust planes;

VSC: Volcanic-Sedimentary Complex; PQG: Phyllite-Quartzite Group; Red line: pre-Devonian horizon; Orange

lines: deep crustal reflectors. Figure ad. from Carvalho et al., 2016 ................................................................ 22

Figure 12. Example of late Variscan faults, represented by strike-slip faults that control basement block

geometry, defined by horst and grabens. Some faults are mineralized, presenting copper veins, mined in the

XIX century. ...................................................................................................................................................... 23

Figure 13. A based on U, Th a K concentrations from an aerospectrometric survey conducted in the SPZ,

where IPB is located, with mining prospecting purposes (Torres et al., 2000) ................................................ 24

Figure 14. Temperature estimation (°C) at 2000 m deep in the IPB Portuguese sector. Geology ad. from


Figure 15. Temperature estimation (°C) at 5000 m deep in the IPB Portuguese sector. Geology ad. from



(A1.2.2) 4 / 38

List of Tables

Table 1. Average thermal conductivities estimated from laboratory measurements of core samples from

boreholes OT1, AL2, FS25, FS26, SDV2 and S32. Average values correspond to the arithmetic average of

values obtained in each borehole for the same formation .............................................................................. 16

Table 2. Assumed average thermal conductivities of some rock materials in boreholes in Mainland Portugal

(from values published in Cermak and Rybach (1982)).................................................................................... 17

Table 3. Borehole list with thermal conductivity measurements made on core samples (Correia et al., 1982;

Almeida, 1993) with (1) effective and (2) assumed thermal conductivity from one measurement on one

single sample. Boreholes S4A and SD27 (Almeida, 1993), effective thermal conductivity is considered to be

the same as for the core samples (see text for explanation) ........................................................................... 17

Table 4. Observed density of outcropping rocks and cores from mining wells from 1 – IGM/SFM; 2 – Lagoa

Salgada Consortium (Soc. Mineira Rio Artezia/EDM); 3 – AGC/Lundin Mining. * – Disseminated

magnetite/dike. Variations in depth related with rock porosity were not considered. A – ITGE data in García

et al., 1998 and Jiménez, 2013 (Matos et al., 2016, in press). ......................................................................... 27

Table 5. Summary of datasets pertinent to CHPM2030 held by LNEG. ............................................................ 30


(A1.2.2) 5 / 38

1 Preface

This report was written as part of the CHPM2030 project “Combined Heat, Power and Metal extraction from

ultra-deep ore bodies” and studies the ability of the Iberian Pyrite Belt for implementation.

The Iberian Pyrite Belt (IPB) is a Variscan metallogenic province located in the SW of Portugal and Spain that

hosts the largest concentration of massive sulphide deposits worldwide (Inverno et al., 2015). It covers about

250 km long and 30–50 km wide (Figure 1) a vast geographical area with particular volcanic and sedimentary

sequences of Carboniferous and Devonian ages, identified in the southwest of the Iberian Peninsula (Oliveira

et al., 2013). The IPB runs from NW to SE, from Alcácer do Sal (Portugal) to Seville (Spain). Since the 1960’s

intense geophysical exploration has been done and discovering new hidden massive sulphide orebodies (like

Neves Corvo (Albouy et al., 1981, Relvas et al., 2006, see Figure 1), Las Cruces (Doyle, 1996) and Lagoa

Salgada (Oliveira et al., 1998).

Figure 1. Location of the central area of the IPB Portuguese sector within the scope of the Iberian Peninsula and main geological groups. Location of the IPB massive sulphide deposits and intense acid mine drainage

(Inverno et al., 2015, Abreu et al., 2010). Active mining: Neves Corvo (Somincor-Lundin Mining) and Aljustrel (Almina). Scale (line): 5 km

Due to the large amount of mineral deposits in southern Portugal (Figure 2) and because of the intensive

deep mining prospecting, a dense borehole network was created, drilled by mining companies (see example

of exploration drill hole distribution in the IPB Portuguese sector in the Figure 3.


(A1.2.2) 6 / 38

Figure 2. Mineral deposits, their morphological type and dimension of Southern Portugal with special focus to the IPB (delimited in purple)

Adequate areas for implementing CHPM2030 “Combined Heat, Power and Metal extraction from ultra-deep

ore bodies” will be briefly studied in this report. Considering the CHPM2030 objectives the Neves Corvo

deposit was selected, considering the deep mining operations (until 900 m depth) and available exploration

drill hole data, until 1800 m depth in the Cotovio sector, located SE of the Neves Corvo mine. Selected drill

core samples will be studied and analysed, to permit a proper characterization of the geological scenario.

The model analysis will be complemented with inferred deep geophysical model, based in the LNEG seismic

profiles (data up to 10 km depth) performed in the EU FP7 PROMINE project.


(A1.2.2) 7 / 38

Figure 3. Central area of the IPB Portuguese sector (ad. Matos and Filipe Eds., LNEG 2013): mineral occurrences – circles: red – massive sulphides, dark purple – Mn, green – Cu, blue – Ba(Pb) and exploration

drill holes (triangles). Map grid: 1:25,000 scale maps (16 km x 10 km).


(A1.2.2) 8 / 38

2 Country specific issues

2.1 Climate

Portugal is mainly characterized by a warm temperate, Mediterranean climate with a distinct wet season in

winter. During winter, Portugal experiences a similar temperature pattern to the Spanish coastal towns, i.e.

average daytime maximum of about 16 °C. Figure 4 resumes these characteristics (http://www.ipma.pt).

2.2 Active mining exploration in IPB

The southern part of the country shows excellent logistics for exploration and mining. There is a considerable

amount of mineral deposits, as seen in Figure 3. Presently, active mining occur at the Neves Corvo mine,

owned by Somincor-Lundin Mining (www.lundinmining.com), and at the Aljustrel mine, owned by Almina

(www.almina.pt). Both mines produce copper ore concentrates from mined massive and stockwork sulphide

ores. In the case of the Neves Corvo mine, zinc and lead concentrates are also produced. The ores are

transported by train and by truck to the Setubal harbour located south of Lisbon and exported worldwide.

Both mines have a strong contribution to regional and national economy.

Figure 4. a) Average annual temperature (°C) and b) Average annual precipitation (mm) (source http://www.ipma.pt).


(A1.2.2) 9 / 38

3 CHPM2030 Goals in the portuguese IPB sector

3.1 Properties to study (stratigraphic, lithological, structural, mineralogical, chemical)

To understand the rock-mechanical and geochemical properties of the IPB ore bodies special measurements

were carried out in exploration drill hole cores, related with different mineralogical, geochemical and

mechanical characteristics of the mineralization and related host rocks. Different scenarios were identified

considering the presence of sedimentary and volcanic rocks of the IPB Volcano-Sedimentary Complex (VSC)

and sedimentary rocks of the Phyllite-quartzite Group (PQG). Considering the IPB geology the following

lithological units were considered:

Mineralization: massive sulphides and stockwork (sulphide vein network);

Upper VSC sediments - siliceous shales, grey shales, green shales, purple shales, cherts,

jaspers and volcanogenic sediments;

Lower VSC sediments – black pyritic shales, black cherts;

VSC felsic volcanics (with and without hydrothermal alteration);

VSC basic volcanics;

PQG sediments – shales, silts and quartzites, forming the IPB basal siliciclastic basement.

Deep exploration drill holes located in the Neves Corvo region were evaluated, considering deep rock

intersections, bellow 1 000 m depth (see drill hole distribution in Figure 2). In the Cotovio sector, located 5

km SE of the Neves Corvo mine, two drill holes were performed by Somincor, bellow 1500 m (see section in

Carvalho et al., 2016). Considering the occurrence of these holes and deep seismic performed by LNEG

(Inverno et al., 2015; Carvalho et al., 2016) a sampling program was prepared to the Cotovio area. Sulphide

mineralization samples were also selected in the Neves Corvo mine.

Considering the presence of structural corridors in the Neves Corvo region, like the Neves thrust, related

with Variscan deformation (Inverno et al., 2015), two scenarios were consider related with the rock samples:

high deformation stages (e.g. shear zones) and less deformation areas.

3.2 Working progress considering project goals

LNEG archive samples were considered like massive ore, with high metal content (~7% Zn and >6% Cu ore

grade). The collected sample was collected at the lower sector of the Corvo pyrite ore lens (Figure 5), at 610

m depth. This sample can be used as reference to the Neves Corvo study representing high metal grade

massive sulphide ore (Figure 6). As non-mineralized example, a LNEG Archive drill-core sample was selected,

related with exploration drill hole campaign, performed by the Redfern company in the Porto de Mel sector,

located in the IPB north western sector (Sado Cenozoic basin, see Oliveira et al., 1998). These samples will

provide preliminary data. The obtained results will be compared with historical data, present in the LNEG

exploration database.


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4.1 Structural settings inferred from geology and geophysics (incl. drilling)

The IPB is composed of two upper Paleozoic age major lithostratigraphic units, the Phyllite Quartzite Group

(PQG), the Volcanic Sedimentary Complex (VSC), which is the focus of the present work (Schermerhorn 1971;

Oliveira 1983, Oliveira et al., 2013). Above the VSC the Baixo Alentejo Flysch Group (BAFG) occurs.

Associated with the VSC dozens of massive sulphide deposits occur related with felsic volcanic rocks and

black shales of lower Carboniferous and upper Devonian ages (Oliveira et al., 2005; Pereira et al., 2008;

Matos et al., 2011; Oliveira et al., 2013; Matos et al., 2014). Hydrothermal halos are present associated with

the massive and stockwork ores. General syntheses on the IPB include those of Strauss et al. (1977); Routhier

et al. (1980); IGME (1982); Barriga (1990); Sáez et al. (1996); Leistel et al. (1998); Carvalho et al. (1999); Junta

de Andalucía (1999); Tornos et al., (2000); Tornos (2006); Oliveira et al. (2005, 2006, 2013); Relvas et al.

(2006). Other general studies deal with stratigraphy (Oliveira 1990; Pereira et al 2007), volcanism (Munhá

1983; Mitjavila et al. 1997; Thiéblemont et al. 1998), structure and regional metamorphism (e.g., Munhá

1990; Silva et al. 1990; Quesada 1998) or the facies architecture of the volcano-sedimentary complex

(Soriano and Martí 1999; Junta de Andalucía 1999; Rosa et al., 2008, 2016). The Baixo Alentejo Flysch Group

well exposed in SW Iberia, represents the infill of a foreland basin, which was developed following a

compressive Variscan tectonic inversion that occurred during the upper Visean and lasted until the upper

Moscovian (Oliveira et al. 1979; Silva et al., 1990; Pereira et al., 2008). The sandy/shale turbidites that filled

the foreland basin had their multiple sources in the SW border of the Ossa Morena Zone, in the IPB and in

the Avalonia plate (Jorge et al. 2012).

Figure 5. Neves Corvo general geological section, adapted from Relvas et al., 2006. Location of the lower sector of the Corvo massive ore lens (blue arrow)


(A1.2.2) 11 / 38

Figure 6. Neves Corvo massive sulphide ore, showing primary banded structures and rich layers of chalcopyrite and sphalerite. Sample collected at 610 m depth

The IPB regional structure is conditioned by a SW tectonic vergence. Globally the geological structures

present an E-W direction in Spain and close to the Portuguese/Spanish border and a NW-SE direction in the

western Portuguese IPB sector. Several complex antiforms are defined, forming VSC-PQG outcropping

lineaments (see in the Portuguese sector the 1/200 000 SGP geological maps, Fls. 7 and 8, Oliveira et al.,

1988 and 1992, Oliveira et al., 2013, Inverno et al., 2015). These structures are present in depth, under

Flysch BAFG sediments and/or Cenozoic age sediments (e.g. Sado Basin, Oliveira et al., 1998). In the northern

IPB regions allochtonous structures are dominant. In the southern IPB branch the complexity is lower. Detail

geological mapping and information of exploration drill holes permit to define the geometry of the VSC-PQG

antiforms. Gravity, magnetic and seismic surveys are useful tools to 3D modelling. As an example see the 3D

models defined to the Rio Tinto (Martin-Izard, 2015) and SE Neves Corvo region (Inverno et al., 2015). The

exploration goals of these programs is to define the constraints related with the presence of massive ore

associated with the VSC volcanism and the presence of stockwork type of ore located both in VSC volcanic

and sedimentary units and PQG sedimentary units. Variscan and late Variscan fault systems are also defined,

in the first case correlated with dominant compressive faults and in the second case related with strike-slip

faults.


The IPB massive sulphides deposits are associated with volcano-sedimentary sequences present in sea floor

environment. Genetic models are present in literature (e.g. Barriga et al., 1997; Leistel et al., 1998; Carvalho

et al., 1999; Tornos, 2006; Relvas et al., 2006, Rosa et al., 2008, 2016) considering hydrothermal events

formed by circulation of sea water in the host rock sequences and later discharge of mineralized fluids.

Regional and hydrothermal alteration occur, the late represented by silica and chlorite in the inner zones and

silica + sericite in the external zones. A significant number of deposits is directly associated with felsic

volcanic rocks formed in the late Devonian (Matos et al., 2011) and early Carboniferous (Barrie et al., 2002;

Tornos, 2006), see Neves Corvo section, Fig. 5. The deposits generally present a lenticular shape with up to 2

km of length and thickness usually < 150 m. The stockwork structures are commonly present in the root of

the hydrothermal system. Variscan tectonics can change the original geometry by folding and faulting,


(A1.2.2) 12 / 38

including thrust generation, promoting the existence of complex structures. The deposits are formed mainly

by massive pyrite. Other minerals occur like chalcopyrite, sphalerite, galena and sulphossalts locally with

economic importance. Present near mining exploration projects, like the Lundin Mining Neves Corvo DGEG

Exploration Permit Area, are being developed and focused in the research of new metal rich massive and

stockwork mineralizations.

4.3 Hydraulic properties, deep fluid flow

According with Batista (2003), water pumping tests performed in the Neves Corvo IPB area (See Figure 1)

and surroundings, conducted by Bertand et al. (1982) in eight wells with maximum depth of 261 m and drill

holes with depths ranging from 100 to 645 m, d concluded that drawdowns to the wells between 0.88 and

21.6 m and to the drill holes between 6 and 43.4 m. Transmissivities have values respectively of between

9.1 x 10-6 and 1.1 x 10-4 to the wells and between 1.86 and 64.6 x 10-6 m2/s to the drill holes.

In the Variscan Massif terrains (north and center of Portugal) the permeability is higher, reaching dozens of

meters per second and is associated to fracturing zones. In these fracturing zones, decompression and

terrain alteration allow a permeability that averagely ranges from 0.1 and 2 x 10-6 m/s. At bigger depths, and

away from the fracturing zones, permeability diminishes, and is lower than 0.01 x 10-6 m/s.

Some conclusions could be taken from these hydrogeological data:

1. The possibility to find an important aquifer in this compact unit pile with low permeability and with

low effective porosity is very low.

2. The deep fractures opened to water circulation are found in the top of the pyrite ore lenses, in the

flysch grewackes from the base and not in the interior of the sulphide ore. These greywackes show

more permeable crushing zones that, instead, can make groundwater circulation easier.

This last conclusion may be important, if these more permeable zones are near the sub-vertical faults that

put the sulphide ore in contact with surface waters. Since the ductile shales are above these graywackes are

much less permeable, making groundwater circulation towards the surface possible only in fracture zones.

Zones with the contact between surface and mineralized ores are located in the Graça Hill and in the main

meander of Ribeira de Oeiras, S of the Neves Corvo Mine.

Through monitoring and surface water control, Fernandez-Rubio y Associados (1994), the hydrogeological

system of Neves-Corvo identified three hydrogeological units:

Upper Shallow System – This system is considered to be an aquifer or an aquitard, free to semi-

confined, relatively heterogenous with permeability decreasing in depth , extends from surface to

100 to 200 meters depth.

Intermediate system – Considered a semi-confined defined in the limit of the previous aquifer, until

the top of the mineralization.

Deep mining system – Confined aquifer composed by the mineralized deposits and overimposed

rocks.

4.4 Fluid composition, brines, meteoric waters

No information available.


(A1.2.2) 13 / 38


The Geothermal Resources Atlas of 2002 (Hurter and Haenel, 2002) has shown that heat flow density (HFD)

values in the central Portuguese IPB are slightly higher than in the rest of the IPB area. This information is

based on thermal properties that have been so far extensively studied in the IPB, using mostly mining data.

Thermal conductivities, geothermal gradients and heat production values based on U, Th and K

concentrations have been determined since 1982 by several research institutions and are processed and

stored in LNEG, which instead makes them available to the general public using interactive internet tools

(http://geoportal.lneg.pt), Atlas Geotérmico de Portugal Continental).

The HFD values for mainland Portugal vary from 40 mW/m2 to 115 mW/m2, with an average value of about

75 mW/m2. HFD values for the CIZ (up north) of the Hesperic Massif ranging from 65 mW/m2 to 80 mW/m2.

In the northern part of the massif there is a HFD increase. In the SPZ, however, regional HFD values reach

about 90 mW/m2, while in the Ossa Morena Zone (OMZ) these values decrease to about 60 mW/m2, which

are similar to HFD values obtained for other European Hercynian regions. In the sedimentary basins, regional

HFD values range from about 40 mW/m2 to 90 mW/m2.Surface HFD in mining, water and geothermal wells is

calculated multiplying the average geothermal gradient obtained in a well by the thermal conductivity of the

geological formations crossed by the well.

A map of HFD Mainland Portugal was created with the information described before (Figure 7).

Figure 7. Heat flow map for mainland Portugal (http://geoportal.lneg.pt)


(A1.2.2) 14 / 38

When determining HFD in these wells it is assumed that the formations crossed by the well are laterally

homogeneous and isotropic, and that the thermal conductivity is independent of temperature. It is also

considered that heat transfer is by conduction and stationary. The effects of heat production by radioactive

decay of thorium, uranium and potassium are also considered. In these wells, HFD is calculated through the

Fourier equation:

q = k (grad T) (1)

where q (W/m2) is the HFD, k is the thermal conductivity (W/mK), (grad T) is the vertical geothermal gradient

(K/m), usually represented in °C/km. Most times the unit mW/m2 is used as a practical unit for HFD.

For this study all data considered reliable for heat flow density estimations had to satisfy several constraints

concerning physical characteristics of the wells, number of temperature measurements in the well, precision

of the temperature measurements, and borehole stability criteria (Ramalho and Correia, 2004).

Figure 8. Geothermal gradient for Mainland Portugal with the IPB sector (http://geoportal.lneg.pt)

Temperature data were collected from different sources. Selected wells were initially studied by Almeida

(1992), Duque (1991), Ramalho (1997); some of them are wells in which temperature measurements were


(A1.2.2) 15 / 38

carried out by Almeida (1992) and processed as described in detail in Ramalho and Correia (2004), creating

national geothermal maps with zoom to the IPB (Figure 8). For those wells where thermal conductivity

measurements were available (Duque, 1991; Almeida, 1993), the effective thermal conductivity was

calculated using those values; otherwise, assumed thermal conductivities were assigned to the rocks, based

on measured values obtained in other samples of the same rock type of nearby wells or, if the thermal

conductivity of the formations is not known, average values mentioned in literature (for instance, in Cermak

and Rybach, 1982) were used. In the wells where no lithology was available, assumed thermal conductivity

was the same as considered in Fernandèz et al. (1995; 1998).

Thermal conductivities were measured in rock samples from boreholes in the IBP. As said before, estimations

of heat flow density use the so called effective thermal conductivity. This was estimated using a ponderation

of the thermal conductivity (laboratory or assumed) of each lithology crossed by the borehole with

corresponding thicknesses. Effective thermal conductivity is estimated through the equation

keffective =

k

z

z

n

1 = i i

i

n

1 = i

i

(2)

Where the index i corresponds to the different rocky materials crossed by the borehole, ΔZ depth of

measurements, and ki is the thermal conductivity. A set of of laboratory measurements of thermal

conductivity in core samples from the IPB (Correia et al., 1982; Camelo, 1987a; Duque, 1991; Almeida, 1993)

made that in most of the mining and water wells considered in this work was carried out through lithological

logs. For each of the boreholes, this study consisted on the attribution of the average value of thermal

conductivity in analogue samples whenever needed. Therefore, to estimate the thermal conductivity of each

formation crossed by a borehole, two ways were used: (1) a value that was measured in laboratory, in a core

sample from that precise borehole or (2) the average value of the thermal conductivities measured in core

samples from analogue formations in other IPB boreholes. For those Portuguese geological formations

without any laboratory measurement of thermal conductivity average values of thermal conductivity for

similar rocks obtained containing physical properties of rocks (Cermak and Rybach, 1982).

Thermal conductivity determination in rock samples was made with a Showa Denko conductivimeter, model

QTM-D2 and the measurements were made in rock samples from 12 boreholes, some of them reflected for

heat flow density determinations (Correia et al., 1982; Camelo, 1987a; Duque, 1991; Almeida, 1993).

Effective thermal conductivity attributed to each borehole was estimated through eq. (1).

The values of estimated average thermal conductivity though thermal conductivity measurements obtained

in laboratory in rock samples from Mainland Portugal are represented in Table 1.

Table 2 shows thermal conductivity values of rocks with no laboratory determinations, but showing assumed

values assigned from literature to estimate effective conductivity. These conductivities are therefore

assumed as representative of the Portuguese geological formations, to which there are not laboratory

thermal conductivities measurements. To those boreholes without lithological logs, assumed thermal

conductivities used by Fernandèz et al. (1995) and later applied in Fernandèz et al. (1998), following identical

criteria in the entire Iberian Peninsula.


(A1.2.2) 16 / 38

Table 3 shows the list of borehole where thermal conductivity measurements were done on core samples

where (1) effective and (2) assumed thermal conductivity was determined from one measurement in one

single sample.

Lithology

Number of measured samples

Number of drill holes

Average value

(W/mK)

Shales and greywackes 22 3 3.69

Shales 2 1 3.03

Black shales (graphitic and pyritic)

1 1 4.16

Shales with Mn veins and disseminations

12 2 4.29

Basic intrusive rock 7 1 3.31

Purple (hematitic) and green shales and siliceous shales

4 1 5.41

Green shales 4 3 4.29

Felsic aphyric volcanics 11 1 3.65

Silicified felsic volcanics 4 1 3.17

Chloritized felsic volcanics 1 1 3.29

Greywackes 6 1 3.48

Quartz dikes 1 1 3.07

Granite 1 1 3.40

Dolomite limestones 5 6 3.83

Mineralized dolomites 4 1 3.88

Limestones 3 1 3.42

Carbonate schists 2 1 3.56

Table 1. Average thermal conductivities estimated from laboratory measurements of core samples from boreholes OT1, AL2, FS25, FS26, SDV2 and S32. Average values correspond to the arithmetic average of

values obtained in each borehole for the same formation


(A1.2.2) 17 / 38

MATERIAL THERMAL CONDUCTIVITY (W/mK)

Silts 2.38

Sandstones 2.30

Diabases 2.45

Talc and serpentinites 3.17

Clay 1.72

Sand 1.57

Argillaceous shales 2.59

Dolomitc shales 4.06

Table 2. Assumed average thermal conductivities of some rock materials in boreholes in Mainland Portugal (from values published in Cermak and Rybach (1982))

REF. COORDINATES CONDUTIVITY (W/mK)

LONG. LAT. 1.EFFECTIVE

2.ASSUMED

S32 7°44’56”W 38°16’40”N 3.85 (1)

OT1 8°11’55”W 37°38’21”N 4.27 (1)

AL1 8°11’56”W 37°36’49”N 3.64 (1)

FS25 8°09’13”W 37°51’25”N 3.46 (1)

FS26 8°08’27”W 37°52’15”N 3.36 (1)

Table 3. Borehole list with thermal conductivity measurements made on core samples (Correia et al., 1982; Almeida, 1993) with (1) effective and (2) assumed thermal conductivity from one measurement on one

single sample. Boreholes S4A and SD27 (Almeida, 1993), effective thermal conductivity is considered to be the same as for the core samples (see text for explanation)

However, some boreholes whose distribution of temperature in depth does not satisfy the previously

mentioned criteria to estimate average geothermal gradient are not selected. This means that none of these

boreholes shows a sufficiently straight score from which that gradient can be estimated. It's also noticeable

that for boreholes where the lithological column is known but there are but there are no determinations in

core samples, each lithological formation was assigned with an average thermal conductivity based in

thermal conductivities measured in core samples from other boreholes (Correia et al., 1982; Camelo, 1987b;

Duque, 1991; Almeida, 1993).

Heat Flow Density estimations (W/m2) for the IPB Portuguese sector is represented in Figure 9.


(A1.2.2) 18 / 38

4.6 Geophysical Exploration surveys in the IPB

The application of geophysical techniques in massive sulphides deposits exploration has been a success in

the Iberian Pyrite Belt province (IPB), both in Portugal and in Spain. Several hidden massive sulphide deposits

associated to the IPB Volcano-Sedimentary Complex (VSC) were discovered in SW Iberia using integrated

interpretation of geological and geophysical models, such as Neves Corvo (Albouy et al., 1981; Leca et al.,

1983) and Lagoa Salgada (Oliveira et al., 1993; 1998a; 1998b) in Portugal, and Valverde (Castroviejo et al.,

1996; Gable et al., 1998) and Las Cruces (Doyle, 1996) in Spain. In the IPB Portuguese sector, regional and

systematic surveys were carried out by the governmental agencies Serviço de Fomento Mineiro

(SFM)/Instituto Geológico e Mineiro (IGM), presently LNEG (Queiroz et al., 1990; Oliveira et al., 1993, 1998a,

1998b, Matos and Sousa, 2008). This public investment and other surveys promoted by exploration

companies, permitted to develop large databases along time in particular methods like gravimetry,

magnetometry (c.f. Figure 10), electrical and electromagnetics. This section of the report presents a brief

description of the geophysical techniques applied in the IPB Portuguese sector, with emphasis on the

regional gravity, magnetic and radiometric surveys.

Figure 9. Heat Flow Density estimations (W/m2) for the IPB Portuguese sector. Geology ad. from http://geoportal.lneg.pt

Geophysical methods have been widely used in the IPB since the early 1940’s. As part of a national

prospecting plan lead by the former SFM (Queiroz et al., 1990) and IGM (Oliveira et al., 1993), both

Governmental Surveys dedicated to the mining industry, several campaigns were performed between the

1950’s and 1990’s. Multiple campaigns were carried out, encouraged by the SFM/IGM activity, the easy data

access and the discovery of several massive sulphide deposits, including the giant Neves Corvo Cu-Zn-Sn

world class rich deposit (Carvalho et al., 1999; Relvas et al., 2006; Matos and Sousa, 2008). The interest of

http://geoportal/


(A1.2.2) 19 / 38

important international investors, like Anglo American (Minaport), Asarco, Atlantic Copper, Billiton, BP

Minerals, Conasa, Elf Aquitaine, Ferragudo Mining, Lundin Mining (Somincor/AGC Minas de Portugal),

Northern Lyon Oy, Redcorp, Redfern, Rio Tinto (Riofinex, Soc. Mineira Rio Artezia), Utah and the consortiums

SPE/SEREM/EDMA and SMS/SEREM/SMMPPA, lead to a continuous investment in geophysical research,

based in ground and airborne surveys (Matos et al., 2016).

Figure 10. (left) Geological map 1:1K (http://geoportal.lneg.pt) (right) Magnetic Total Magnetic Field Intensity map with reduction to pole, based on RTZ survey, ad. Represas et al. 2016

In some areas the technical support was provided by the SFM, IGM and LNEG teams (Matzke, 1971; Albouy

et al., 1981; Leca et al., 1983; Castelo Branco, 1995; La Fuente, 1995; Carvalho et al., 1996; Castelo Branco,

1996; Palomero and Mora, 1996; Castelo Branco and Sá, 1997; Palomero, 1999; Mora, 2002; Faria, 2007;

Matos et al., 2009a, 2009b; Araujo and Castelo Branco, 2010; Carvalho et al., 2011). National companies like

the Emp. De Desenvolvimento Mineiro, Emp. Desenvolvimento Mineiro do Alentejo, Emp. Mineira Serra do

Cercal, MAEPA, Portuglobal and Pirites Alentejanas invested also in different geophysical campaigns. A

significant volume of exploration works were made by several junior mining companies, investing in the

characterization of drill targets defined in the geological structures with high mining potential. Specialized

consulting companies worked at IPB, improving data treatment and interpretation techniques – e.g. Adaro,

Anglo American (Minaport), Bundesanstalt für Geowissenschaften und Rohstoffe, Condor Consulting,

Compagnie Générale de Géophysique, Geoconsult, Geoterrex, Institut für Geofhysik TU Clausthal, Int.

Geophysical Technology, La Montagne SAP, Lea Cross Geophysics, Lab. Geopphysique Aplliqué et Structural,

Univ. Nancy, Soc. Mineira Rio Artezia/Rio Tinto Zinc, Sanders Geophysics and Urguhart-Dvorak. The SFM,

IGM and LNEG teams worked for various mining companies as geophysical consultants (gravity, magnetic,

seismic and electric surveys), being examples the collaborations with MAEPA, Northern Lion Oy, Somincor

and Soc. Mineira Rio Artezia.

The first geophysical method used in the Portuguese sector of the IPB was the electromagnetic Turam

technique, with some initial essays in the early 1940’s (Queiroz et al., 1990). The real geophysical

prospecting activity only started in the early 1950’s by the continuous work of the SFM teams, especially

near the active main mining areas of Aljustrel and São Domingos, respectively operated by Mine d’Aljustrel

(Leitão, 1998; Martins et al., 2003) and Mason and Barry (Matos et al., 2006) companies. The discovery in

1954 of the superficial part of the Aljustrel Moinho massive sulphide sub vertical orebody (Leitão, 1998),


(A1.2.2) 20 / 38

named Carrasco, represents the first successful application of the Turam method. This positive result

promoted the SFM regional campaigns dedicated to the exploration study of the areas were the VSC and

Phyllite-Quartzite (PQ) (Givetian-Strunnian age) formations outcrop (Pereira et al., 2008; Matos et al., 2014;

Matos et al., 2016). The methodology was consisted of dozens of NE-SW parallel Turam profiles, parallel to

the VSC and PQ geologic structures. In the 1950’s the magnetic method started to be used but the lack of

signature of some orebodies opened way to other geophysical methods.

After the preliminary Turam and magnetic surveys, the gravimetric method became the main tool to detect

new sulphide masses in the IPB. Until 1960’s the role of the SFM was unique, based in detail ground surveys

carried out over N-S, E-W grids with spacings of 200 m, 100 m and 50 m (Queiroz et al., 1990; Oliveira et al.,

1993). The discovery of the Aljustrel Feitais orebody in 1964 (Leitão 1998; Martins et al., 2003) by Mines

d’Aljustrel using gravity surveys showed the potential of this method. Later, the introduction of electrical

methods improved the quality of the resistivity data, since they provided deeper and more reliable informa-

tion than Turam. Underground gravity surveys were performed at the Lousal mine in the late 1960’s

(Matzke, 1971). The discovery of the Neves Corvo ores in 1977, as a direct result of the exploration work of

mining companies, as well as previews of SFM exploration surveys (Carvalho, 1982; Leca et al., 1983;

Carvalho et al., 1999; Oliveira et al., 2006; Matos et al., 2016), show the advantages of an integrated model

interpretation, as it included the study and interpretation of geological structures based on the use of elect-

rical resistivity and spontaneous potential simultaneously, followed by magnetics and gravimetric surveys.

The extreme copper grades of the Neves Corvo deposit justified more investment in exploration, including

deep structures (>500 m depth). Considerable efforts were developed in some areas like the Neves Corvo-

Corte Gafo, a 600 km2 polygon (Carvalho et al., 1996), were Somincor developed a multidisciplinary program:

gravity + magnetic surveys (9015 points distributed covering an area of 314.5 km2, with technical support of

the SFM gravity team) and several profiles of transient electromagnetic (TEM, 215.5 km), magnetotelluric

(27.0 km) and seismic reflection (24 km). Detail works were performed at Neves Corvo, João Serra and Corte

Gafo areas, including down hole geophysical log: 2 000 m of resistivity + sonic surveys and 2 500 m of TEM

surveys.

High logistic costs and the development of differential GPS topographic techniques promoted the change of

ground gravity and magnetic surveys in 1990’s from the regular grids to random grids with ~300 m spacing.

The Rio Tinto Company was the first to apply this geometry in the region, after test programs developed in

well-known areas like Águas Teñidas (Spain) (Castelo Branco, 1995; Braux et al., 1996; Castelo Branco and Sá,

1997). Rio Tinto and others companies like Minaport (Anglo American), also promoted, during that decade,

the achievement of regional magnetic and radiometric airborne surveys (La Fuente, 1995; Castelo Branco,

1995; Castelo Branco and Sá, 1997; Torres and Carvalho, 1998). At a local scale, other geophysical methods

are being used to characterize gravity and geological targets. Aiming at specific goals in well-defined targets,

methods such as deep reflection seismic, electrical resistivity, induced polarization, TEM, VTEM, vertical

electrical soundings and magneto-telluric have been applied. In massive sulphide mineralized structures

down-hole surveys (e.g. Mise à La Masse, TEM) were essential to follow the mineralization trends, like in the

Lagoa Salgada (Oliveira et al., 1993, 1998a) and Semblana (Araujo and Castelo Branco, 2010) sectors.

Stockwork vein type mineralizations can also be identified using these methods, like the recent cases of the

Serrinha induced polarization profiles (NW IPB sector, see Figure 1, Ramalho and Matos, 2009; Matos et al.,

2009) and Chança, Montinho and Caveira massive sulphide orebodies detail exploration studies performed

by Sociedade Mineira Rio Artezia (Mora, 2002) and Atlantic Copper (Palomero, 1999). At the Neves Corvo


(A1.2.2) 21 / 38

region, seismic profiles were used by Lundin/Somincor to define key tectonic structures (Araujo and Castelo

Branco, 2010; Inverno et al., 2013, 2015; Matos et al., 2016).

The Neves Corvo deposit presents a gentle inclination to NE, with seven orebodies dispersed in a large

complex antiform structure (Araujo and Castelo Branco, 2010; Oliveira et al., 2013). The correct

understanding of the geometry of the study area implies a significant detail in the geological mapping based

in surface surveys and/or drill holes logging (Matos et al., 2016). In areas with few drill-holes, the geophysical

data can be essential to model construction. The geophysical and geological data integration using 3D model

software is essential to define target zones in future drill campaigns. However, as potential field data

modelling/inversion are an ill-posed problem and no unique solution exists, seismic reflection is often used

to provide structural information (together with drill-hole and geological data), thus reducing the ambiguity

of modelling/inversion. This strategy is being used with success by Lundin Mining in the Neves Corvo region,

with 3D seismic reflection surveys acquired over existing massive sulphide ores (e.g. Lombador) and defining

new targets, as the recent Semblana and Monte Branco discoveries (Araujo and Castelo Branco, 2010;

Lundin Mining website, Feb. 2016, http://www.lundinmining.com/).

3D models based in geophysical, geological and drill-hole data are being defined for the IPB deposits of

Neves Corvo (Inverno et al., 2013; Batista et al., 2014; Inverno et al., 2015), Caveira (Matos et al., 2015),

Lagoa Salgada (Represas and Matos, 2012) and Rio Tinto (Martin-Izard et al., 2015). Data compilation and

reprocessing of geophysical data in the regions is also being undertaken by private companies and

governmental agency (LNEG) due to the development of new data processing techniques and computing

advances.

Recently, 81 km of deep 2D seismic reflection data (up to 10 km) were acquired by LNEG/Prospectiuni

between Neves Corvo and the Spanish border, to check the prolongation of the IPB volcanic axis to SE and its

connection with the Spanish side of the IPB (Carvalho et al. 2016) (Figure 1). This dataset was interpreted in

a 3D environment using gravimetric, radiometric, magnetic, drill-hole and surface geological data and it was

possible to follow the volcanic axis from Neves Corvo till Spain and estimate its depths which are at places

compatible with present day exploration (Figure 5, Figure 11 and Figure 12).

After 70 years of exploration work, a large area of the IPB is already covered with several geophysical

methods. A large amount of acquired data is standardized and supervised by LNEG. Considering the IPB as an

important base metals mineral province the mineralization targets are defined by massive/semi-massive

sulphide ore lenses, stockwork veins and disseminated mineralizations with hydrothermal halos, present in

VSC felsic and shale units (Carvalho, 1982; Matos et al., 2011; Matos et al., 2016).

http://www.lundinmining.com/


(A1.2.2) 22 / 38

Figure 11. Gravimetric and magnetic data a) plotted over CRS stack for seismic profile 1 without b) and with post-stack time migration with overlaid stratigraphic and structural interpretation c). The locations of drill-

holes CT01 and CT08001 are shown (blue line) and a geological cross-section based on these two drill-holes and previously acquired seismic reflection data is overlaid the interpreted stacked section. Mfi: Magnetic

field intensity (reduced to the pole); Ba: Bouguer anomaly. Black lines: faults; Yellow lines/T: thrust planes; VSC: Volcanic-Sedimentary Complex; PQG: Phyllite-Quartzite Group; Red line: pre-Devonian horizon; Orange

lines: deep crustal reflectors. Figure ad. from Carvalho et al., 2016


(A1.2.2) 23 / 38

Figure 12. Example of late Variscan faults, represented by strike-slip faults that control basement block geometry, defined by horst and grabens. Some faults are mineralized, presenting copper veins, mined in the

XIX century.


(A1.2.2) 24 / 38



Temperature in depth maps obtained with geothermal mapping together with thickness, transmissivity, and

fluid chemical characteristics also in depth will have a significant importance in the entire process to evaluate

areas with more accurate methods and additional resources. Therefore, temperatures at 1000, 2000 and

5000 m are estimated, following heat flow density estimations (from average thermal conductivity and

geothermal gradient) and heat production values (A) (Haenel et al., 1980), based on spectrometric

concentrations of U, Th and K, mostly from Rybach and Cermack (1982), Correia (1995) and

aerospectrometric surveys for mining prospecting. (Figure 13) shows a map of A based on U, Th a K

concentrations from an aerospectrometric survey conducted with mining prospecting purposes.

Figure 13. A based on U, Th a K concentrations from an aerospectrometric survey conducted in the SPZ, where IPB is located, with mining prospecting purposes (Torres et al., 2000)

In this case, the step model was used.

T(z) – T0 = q zk +

A z2

2 k (3)

where T(z) is the temperature at depth z (°C), T0 is the average surfarce temperature on Earth (°C), z is the

depth (m), A is the heat production per unit of volume (Wm-1K-1) and k is the thermal conductivity (Wm-1K-13)

Whenever possible, considered temperature was the measured temperature or interpolated between two

measured temperatures, such as the case of onshore and offshore boreholes. In case of its inexistence,

temperatures were extrapolated to bigger depths from shallower depths. The first was used only in several

oil wells, after bottom bole temperatures correction for thermal disturbances caused by drilling (Haenel et

al. 1988).


(A1.2.2) 25 / 38

HFD from geothermometers was not used for the IPB area, although its values were considered at national

level, since there was information enough about k and A. Generally, temperatures in depth are higher in the

Lusitanian Basin and in the SPZ, where the IPB is located.

Temperatures at 1000 m depth for the IPB are represented in http://www.geoportal.pt, in the Atlas de

Geotérmico de Portugal Continental group of layers, reaching about 40 °C in the IPB, estimated with the

methods described previously. This value is confirmed by Nelson Pacheco (Lundin Mining oral

communication, 2016) to the lower levels of the Neves Corvo Mine, about 900 m deep.

Figure 14. Temperature estimation (°C) at 2000 m deep in the IPB Portuguese sector. Geology ad. from http://geoportal.lneg.pt

Temperatures at 2000 m depth for the IPB are in Figure 14, and can reach about 63 °C in the IPB. Estimated

temperature in the area for 5000 m deep, using the previously described methods for geothermal

investigation is about 132 °C (Figure 15).

Existing temperature in depth models and structural models in IPB can be jointly interpreted with structural

models suggested for the area, based on several types of geophysical data (e.g., magnetic, magnetotelluric).

5.2 Knowledge gaps and limitations

Within the framework of CHPM2030, there is some work to be done in this first task. Information on fluid

composition, brines and meteoric waters is still missing as more representative samples from the Neves

Corvo Mine can also be part of the project. Lundin Mining Company confirmed the technical support to the

LNEG CHPM2030 project. This procedures will allow to the planned drill hole sampling, focused in deep rock

intersections bellow 1000 m depth (e.g. Cotovio sector).

http://geoportal.lneg.pt/


(A1.2.2) 26 / 38

Figure 15. Temperature estimation (°C) at 5000 m deep in the IPB Portuguese sector. Geology ad. from http://geoportal.lneg.pt


(A1.2.2) 27 / 38

6 Discussion and concluding remarks

Geothermal gradient, HFD estimations and consequently temperatures in depth obtained for the different

depths, published along the years are considerably different from those presented in the Atlas of

Geothermal Resources in the European Community, Austria and Switzerland” (Haenel and Staroste, 1988),

resulting in the establishment of narrower criteria to select adequate thermometric wells to assure a good

data set quality for the entire Iberian Peninsula, IPB included. The last edition of the “Geothermal Resources

Atlas of Europe” (Hurter and Haenel, 2002), incorporates this dataset and added some thermometric

boreholes drilled with specific geothermal purposes near the IPB.

According with Heat Flow Density Commission this approach is reliable and quality of data is improved as

more information is acquired. The geothermal database followed the format described in Ramalho (1999)

and follows as much as possible the standards defined by the International Heat Flow Commission (Jessop,

1990).

Table 4 shows the observed density in outcropping rocks and cores from several mining wells.

Unit Rock type Observed

density Density (ITGE data)a Studied sectors (Portugal)

Mér

tola

Flys

ch

Shales and greywackes

2.70-2.81 2.66-2.68 Taralhão 1

Vo

lcan

o-

Sed

imen

ary

Co

mp

lex

Siliceous shales 2.65-2.77 2.65 Rio de Moinhos 1

Green/purple shales 2.58- Rio de Moinhos 1

Black shales 2.81 Rio de Moinhos 1,2

Jaspers and cherts 2.73-2.98 2.63-3.06 Rio de Moinhos 1

Basic volcanics 2.73-2.89 2.78-3.00 Lagoa Salgada 1,2

Acid volcanics 2.58-2.90 2.61-2.68 Lagoa Salgada 1,2

Sulp

hid

e

min

eral

izat

ion

Acid volcanics + hydrothermal alteration

2.63-2.96 Lagoa Salgada 1,2

Stockwork zones 2.88-3.,91 Lagoa Salgada, Rio de Moinhos 1,2

Semi-massive pyrite 2.25-3.54 Lagoa Salgada 1,2

Massive pyrite 4.29-5.03 Lagoa Salgada 1,2

Ph

yllit

e-

Qu

ar-

tzit

e G

r. Shales and quartzites 2.58-2.67 2.56-2.65 Chaparral, Lameira 1

Dark grey shales 2.62-2.84 Chaparral, Lameira, Rio de Moinhos 1

Limestones 2.79 Rio de Moinhos 1

Table 4. Observed density of outcropping rocks and cores from mining wells from 1 – IGM/SFM; 2 – Lagoa Salgada Consortium (Soc. Mineira Rio Artezia/EDM); 3 – AGC/Lundin Mining. * – Disseminated

magnetite/dike. Variations in depth related with rock porosity were not considered. A – ITGE data in García et al., 1998 and Jiménez, 2013 (Matos et al., 2016, in press).


(A1.2.2) 28 / 38

6.1 How the Iberian Pyrite Belt Neves Corvo sector can positively contribute to the aims of CHPM2030

The Neves Corvo mine site includes > 300 Mt of sulphide ore, distributed in 7 ore lenses. The Neves, Corvo,

Graça, Zambujal and Lombador deposits are being mined until 900 m depth by Somincor/Lundin Mining. A

large exploration database, including deep drill holes (above 1 500 m deep) allow the definition of an

accurate setting of the geological model. This data can be correlated with seismic profiles than can predict

the tectonic structures until 10 km depth. All these data are essential to CHPM2030 objectives, considering

the EGS thematic in an active mine site. The Neves Corvo samples study will be shared by LNEG and Miskolc

teams.

After a revaluation of the available information from Lundin Mining, extra material, comprising deeper and

eventually more representative samples from the Neves Corvo mine will be studied.


(A1.2.2) 29 / 38

7 Datasets pertinent to CHPM2030 held by LNEG

Datasets Short description Scale Coverage Access cost Link

Hydrogeology

Hydrogeological maps Regional mapping, fl. 7 and 8. 1:200,000 South Portugal, Alentejo and Algarve regions

See web page http://www.lneg.pt

Geophysics and remote sensing

Gravity Regional map, Bouguer 2.6 1/400,000 (available in the end of 2016)

1:400,000; 1:25,000;

1:5,000

South Portugal, Alentejo region


Airborne magnetics Regional map (available in the end of 2016)

1:400,000 South Portugal, Alentejo region


Airborne radiometrics

Airborne survey data for the radioactive isotopes Th, U, and K, total count. Total count regional map (available in the end of 2016)

1:400,000 South Portugal, Alentejo and Algarve regions


Land gravity A database of over >300,000 gravity observations.

N.A. South Portugal, Alentejo and Algarve regions


Geophysical borehole logs An archive of geophysical downhole log data.

N.A. Various See web page http://www.lneg.pt

http://www.lneg.pt/

http://www.lneg.pt/

http://www.lneg.pt/

http://www.lneg.pt/

http://www.lneg.pt/

http://www.lneg.pt/


(A1.2.2) 30 / 38

Datasets Short description Scale Coverage Access cost Link

Boreholes

Borehole database A database of over one million records of boreholes, shafts and wells.


See web page and LNEG Geoportal

http://www.lneg.pt


Geochemistry

Soil and stream sediments Geochemical database and physical samples


See web page and LNEG Geoportal

http://www.lneg.pt


Table 5. Summary of datasets pertinent to CHPM2030 held by LNEG.

http://www.lneg.pt/


http://www.lneg.pt/



(A1.2.2) 31 / 38

8 Acknowledgements

The authors of this document wish to thank Lundin Mining, especially Dr. Nelson Pacheco, Chief Geologist of

the Neves Corvo mine, for all echnical support to the CHPM 2030 LNEG team. We also thank Augusto Filipe

for sharing figures related with the SIORMIN database and Patrícia Represas from LNEG for density data.

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Web links

http://geoportal.lneg.pt

http://www.lundinmining.com


REPORT ON DATA AVAILABILITY – ROMANIA

Summary:

This document provides a review of the existing data which can substantiate further research

that has, as a final objective, the prepration of a pilot aiming to use the potential of metal

extraction together with geothermal water.

Authors:

Diana Perșa, researcher, Ștefan Marincea, senior researcher, Albert Baltreș, senior

researcher, Constantin Costea, senior researcher, Delia Dumitraș, senior researcher,

Gabriel Preda, GIS editor (Geological Institute of Romania)

This project has received funding from the European Union’s Horizon 2020 research and

innovation programme under grant agreement nº 654100.


Table of contents

1 Executive summary ................................................................................................................................... 5

2 Introduction and outline of work .............................................................................................................. 6

2.1 Goals ................................................................................................................................................. 6

2.2 Country specific issues ...................................................................................................................... 6

3 Previous research and available data ........................................................................................................ 8

3.1 Structural evolution, deep-seated faults and fracture zones, their alignment ................................. 8

3.1.1 History of research ....................................................................................................................... 8

3.1.2 Regional tectonic influenced the formation of North Apuseni Mountains .................................. 9

3.2 Structural settings of North Apuseni Mountains ............................................................................ 13

3.2.1 Study case perimeter ................................................................................................................. 14

3.2.2 How Bihor Mountains can positively contribute to the aims of CHPM2030 .............................. 21

3.2.3 Limitations in our current understanding of Bihor Mountains ................................................... 21

3.3 Geometry and composition of ore deposits ................................................................................... 21

3.3.1 Evolution of banatitic magmatism of Bihor Mountains .............................................................. 22

3.3.2 Banatitic metallogenesis in Apuseni Mountains ......................................................................... 25

3.3.3 Chemical composition and origin of banatites ........................................................................... 27



3.4 Hydraulic properties, deep fluid flow ............................................................................................. 31

3.4.1 Lithology of karst in Bihor Mts ................................................................................................... 31

3.4.2 Short hystorical review of the Bihor Mountains karst hydrology investigation .......................... 32

3.4.3 Orohydrography of the Bihor Mountains ................................................................................... 33

3.4.4 Karst systems ............................................................................................................................. 33

3.4.5 Hydrogeology of karst areas ....................................................................................................... 33

3.4.6 Geological and hydrogeological characteristics of Beiuș geothermal reservoir ......................... 34

3.5 Fluid composition, brines, meteoric waters ................................................................................... 34



3.6 Thermal properties and heat flow .................................................................................................. 35



3.7 Current metallogenetic models (2D- and 3D-) ............................................................................... 37


3.7.1 Pietroasa and Budureasa sites ................................................................................................... 37

3.7.2 Băița Bihor site ........................................................................................................................... 41



4 Identifying target sites for future CHPM ................................................................................................. 45

4.1 Extending existing models to greater depth, integrating data down to 7 km ................................ 45

4.1.1 Magnetic and gravity contributions to the deciphering of banatitic structures ......................... 45

4.1.2 Geological contributions to the deciphering of banatitic structures .......................................... 48


4.2 Limitations in our current understanding of Bihor Mountains ....................................................... 50

5 Concluding remarks................................................................................................................................. 51

5.1 Geological data ............................................................................................................................... 51

5.2 Geophysical and structural data ..................................................................................................... 51

5.3 Hydrogeology ................................................................................................................................. 51

5.4 Metallogenesis ............................................................................................................................... 52

5.5 Geothermal data ............................................................................................................................ 52

6 References .............................................................................................................................................. 53

List of figures

Figure 3.1 Geological setting of the Apuseni Mts (grey). The Moesian platform and the European foreland are

forming the pre-Alpine continental basement. Dark grey (within the Apuseni Mts) shows the suture between

the two microplates Tisia and Dacia. The dashed line is the prolongation of the suture in the Transylvanian

basin, covered by Neogene sediments, Schuller (2004) .................................................................................... 9

Figure 3.2 Correlation between Mega-Units and structural units of the Apuseni Mts. Reproduced from

Merten et al., 2011. ......................................................................................................................................... 10

Figure 3.3 Cross–section illustrating deformation and magmatism processes in the Apuseni Mts (Marten et

al, 2011) ........................................................................................................................................................... 12

Figure 3.4 Simplified Alpine structure of the Apuseni Mountains from Ionescu et al. (2009) compiled by C.

Balica from papers by Ianovici et al. (1976), Bleahu et al. (1981), Săndulescu (1984), Kräutner (1996), and

Balintoni & Puște (2002) .................................................................................................................................. 13

Figure 3.5 Tectonic map of Apuseni Mountains. .............................................................................................. 14

Figure 3.6 Study case perimeter map – edited in GIS by Gabriel Preda, after Geological map of Romania.

Scale: 1:200,000. (Source: Geological and Geophysical Institute, authors: Bleahu, Savu, Borcoș for Brad Sheet

and M.Lupu, Borcoș, Lupu, Bitoianu for Simleul Silvaniei Sheet) ..................................................................... 16

Figure 3.7 Map of vertical gradient of magnetic anomaly (TZ) from Beiuș Basin ............................................. 20

Figure 3.8 Extension of the Banatitic Magmatic and Metallogenic Belt. Romania, Eastern Serbia and Bulgaria

(with dark gray in the inset and with heavy outline in the map). Simplified after Cioflica and Vlad (1973) ..... 22


Figure 3.9 Map showing the distribution of the banatites in the Apuseni Mts (Ștefan el al. 1992, modified

after Borcoș, with aditional data)..................................................................................................................... 23

Figure 3.10 Regional distribution of the mineralization types in the Apuseni Mountains (Stefan et al. 1986). 26

Figure 3.11 Hydrogeological map of the Bihor Mountains kast areas (Orășeanu et al., 2010), according to the

works of Bleahu et al., 1981, Bordea & Bordea, 1973, and to the sheets Avram Iancu (Dumitrescu et al.,

1977), Poiana Horia (Bleahu et al., 1980), Pietroasa (Bleahu et al., 1985), Rãchițele (Mantea et a., 1987) and

Biharia (Bordea et al., 1988) of the geologic map of Romania, scale 1: 50,000 ............................................... 32

Figure 3.12 Extract from geothermal map of Romania (Institute of Geology and Geophysics, 1985). Only a

fragment of the north – western part of the country was included, showing the situations for Apuseni Mts. 36

Figure 3.13 Heat flow distribution on the Romanian territory; contours in mW m-2. Dots represent surface

heat flow data points (after Demetrescu et al,1991) (Demetrescu and Maria Andreescu, 1994) ................... 38

Figure 3.14 Sketch representing Baita Bihor Cu (Mo, Zn-Pb) skarn location (Ciobanu et al. 2002). Deeper parts

of Antoniu have grades of 1-2g/t Au in bornite ore, also rich in Ag, and Bi. 2 Mt of Gold are target for the

present exploitation. ........................................................................................................................................ 42

Figure 3.15 Cross-section representing Baita Bihor Cu (Mo, Zn-Pb) skarn location (Ciobanu et al. 2002). The

intersection of the Antoniu and Blidar faults is considered the main control for this trend (mine geologist O.

Kiss) .................................................................................................................................................................. 43

Figure 4.1 Distribution of depth banatitic structures deduced from aeromagnetic and gravity data (Andrei et

al., 1989) - legend on the next page ................................................................................................................ 46

Figure 4.2 Geophysical data projected on the study case perimeter map ....................................................... 48

Figure 4.3 Cross-section between Codru Moma Mts – Beiuș Basin – Bihor Mts extracted from the profile 1-A

(Ștefănescu et al.). Legends on next page ........................................................................................................ 49

List of tables

Table 3.1 (next pages): Major and trace element concentrations in the Pietroasa, Budureasa, and Băița Bihor

(Bihor Mts) whole-rock samples ...................................................................................................................... 28

Table 3.2 Whole-rock Rb–Sr isotopic data for the North Apuseni Mts (Auwera et al, 2015) ........................... 30

Table 3.3 Chemical composition (mg/l) for well F-3001, Beiuș ........................................................................ 35


1 Executive summary

In order to established an enhanced geothermal system on a deep metal-bearing geological formation a

study case perimeter was selected having some basic conditions fulfilled:

o Important geothermal resources are already exploited in Beiuș basin.

o This region has high heat flow values.

o The geothermal aquifer has a short recharging period of time, being supplied by water coming from

the extensively karstified area of Bihor Mountains.

o Existence of magnesian skarns containing B, Cu (Mo, Zn-Pb), generated in the metasomatism contact

aureola of a batholith with regional extension.

o This granodioritic-granitic batolith and its apophyses, which is the result of Late Cretaceous

magmatism, determined the formation of several ore-deposits within North Apuseni Mountais,

deposits that are included into Banatitic Magmatic Metallogenetic Belt.

o It is possible that three of the most important mineral deposits, Pietroasa, Budureasa and Băița

Bihor, to provide the metals for the envisaged Enhanced Geothermal System (EGS).

o Existence of a clear structural connection between the geothermal aquifer and the selected deep

metal-bearing geological formation.

Within this deliverable the existing data were synthesized and can substantiate further research. The final

objective is the preparation of a pilot which aims on extracting metals together with geothermal heat.



2.1 Goals

The paper aims to present and analyse relevant scientific research in the Bihor Mountains, being a part of

Banatitic Magmatic Metallogenetic Belt (BMMB) of Romania. These studies should be the base for further

investigations that can contribute assessing the creation of an EGS – orebody system. The objective of this

task is to summarize previously reported studies of the uppermost crust of the Earth, reflecting the current

knowledge regarding geology, geothermal potential, prospecting, deep drilling, and geophysical surveys of a

region that offers pre-conditions for the application of the CHPM concept. Knowledge gaps and limitations

should be highlighted for the Bihor Mountains.


Romania has metalliferous deposits that were exploited in the past, or which, for now, were only highlighted,

waiting for a modality by which they can be exploited. Romania also has geothermal resources, insufficiently

valorised.

CHPM2030 project is an excellent opportunity to investigate the possibility of realizing a combination of the

two types of resources, in order to exploit them profitably. For this, a perimeter has been chosen, which,

according to preliminary data that we have, offers sine qua non pre-conditions for further investigations of

the possibility to achieve the objectives of the project.

The perimeter offers the following advantages:

o Mineral resources well studied and documented,

o Geothermal resources in operation, which have already assured the supply of heat and hot water for

several districts of a town,

o Accessibility in the region,

o Available manpower.

This perimeter is considering the geothermal resources from Beiuş Basin, and, also, the existence of a pluton,

which outcrops in the nearby areas, such as Pietroasa, and Budureasa. Perimeter is located in the North of

the Apuseni Mountains and structural units concerned are the Beiuş Depression, and Bihor Mountains.

This report is mainly a compilation of the relevant data which can contribute in reaching a conclusion

regarding the potential of extracting metals in combination with the exploitation of geothermal water.

There are several main elements that led to selection of this perimeter, namely:

The existence, as a result of Late Cretaceous magmatism, of a granodioritic-granitic batholith that

crops out only on restricted areas, among which Pietroasa and Budureasa are better documented,

and is also associated to andesitic and rhyolitic minor intrusions. The intrusion of the banatites has

resulted in contact processes that concerned the sedimentary deposits being traversed. At the

contact of the banatites with the limestones, marbles and various types of calcic skarns have been

formed, while at the contact with the detritic and pelitic rocks, hornfels, garnet skarns, etc. are met.

From genetical point of view, the geochemical spectrum of banatitic mineralization in the Apuseni

Mts is as follows: B, Cu (Mo, Zn-Pb).


The existence of a geothermal anomaly, which is not as important as the one from the Pannonian

Plain, but which is confirmed in Beiuș basin. Within Beiuș Basin, the geothermal water, with

temperatures of 84°C, is extracted from depths of 2700 m.

Regional structural cross sections indicate the extent of batolith under Beius basin, leading to the

hypothesis that it could be a possible source of metal, for the exploitation plant of the metals –

geothermal water complex.

Gravimetric and magnetometric maps also indicate the existence of the batolith under the

sedimentary basin of Beiuș.



3.1 Structural evolution, deep-seated faults and fracture zones, their alignment

In order to consider achieving of an EGS – ore body system, a region that meets to a greater extent several

pre-conditions have been chosen. This is represented by Beiuş Depression, and Bihor Mountains situated in

the North Apuseni Mountains.

3.1.1 History of research

Since 1774 when Ignatz Edlen von Born makes the first mineralogical records, and then researches of I. E.

Fichtel, I. Ruprecht, P. Partsch, Fr. Hingenau, L. Neugeboren etc, consist of petrografic and mineralogical

descriptions of mineralisation deposits occasionally examined. In parallel, stratigraphy and paleontology

notes start to appear, and in 1822 S.F. Beudant realises the first general geological map of the Apuseni

Mountains.

A first embodiment is the valuable monograph on the geology of Transylvania, developed by F. Hauer and G.

Stache 1863, which contain extensive descriptions of the Apuseni Mountains.

Geological researches of Bihor Mountains, mostly related to deposits of useful minerals have begun since

the 19th mid-century. Baita Bihor area benefits from the research of K. Peters (from 1861 to 1862) and Fr.

Pošepny (1873).

During 1889-1890 G. Primics realised the geological mapping of the central area of the Bihor Mountains,

while M. Pálfy (1897-1899) realised the eastern part, and J. Szádeczky (1904-1907) was in charge with the

northern area and Vlădeasa Massif. Since 1905 P. Rozlozsnik deciphers Biharia massive structure.

Since 1950 North Apuseni Mountains were the subject of detailed geological mapping. Thus, in Bihor

Mountains mappings of crystalline basement were conducted by R. Dimitrescu, M. Borcoş, I. Hanomolo, E.

Stoicovici, Aurica Trif, I. Mârza, C. Ionescu and H. Savu.

Sedimentary were clearly defined as follows: Permian was correlated by M. Bleahu, Triassic formations have

been the subject of studies realised by D. Patrulius, M. Bleahu, S. Bordea, Josefina Bordea, Stefana Panin,

Camelia Tomescu, D. Istocescu, Jurassic formations were studied by D. Patrulius and E. Popa and the

Cretaceous formations by D. Patrulius, S. Bordea, Gh. Mantea and D. Istocescu. Neo-Cretaceous post

tectonic basins formations have been the subject of studies conducted by Denisa Victoria Todirica -

Mihailescu Lupu and the Neozoic were investigated especially by D. Istocescu.

Within Bihor Mountains, Codru nappe system was defined and specified by M. Bleahu and the Biharia nappe

system by R. Dimitrescu and M. Bleahu.

Banatitic rocks from North Apuseni Mountains were mapped in detail by A. Ştefan and Gh. Istrate, and the

phenomena of metamorphism and mineralization have been the subject of the research of G. Cioflică, V.

Şerban, S. Stoici, C. Lazăr, M. Borcoş etc.

The research mentioned above, allowed the synthesis and development of cartographic representations that

give a good overview of the structure and tectonic of the Apuseni Mountains and the geological map of the

Apuseni Mountains scale 1: 200 000, was printed in the years 1967 to 1969. The map is accompanied by a

text that containing summaries of stratigraphy, petrography and tectonic of the region. Apuseni Mountains,

in a final assembly work is the guiding text of the Tectonic Map of the Carpatho-Balkan space, published in

1974 in Bratislava.


In 1976 the synthesis ‘Geology of Apuseni Mountains’ was publiched, having Ianovici V., Borcoș M., Bleahu

M., Patrulius D., Lupu M., Dimitrescu R., Savu H., as authors.

In 1985 the geological map of Pietroasa, scale 1: 50,000, elaborated by M. Bleahu et al. was printed by IGR.

3.1.2 Regional tectonic influenced the formation of North Apuseni Mountains

Apuseni Mountains have an isolated position within the Alpine-Carpathian-Dinaride orogen, amidst the

Pannonian basin to the north and west, the Transylvanian basin to the east and the South Carpathians to the

south. The Apuseni Mountains are located at the boundary between the continental Tisza and Dacia tectonic

Mega-Units (e.g. Csontos and Vörös, 2004; Schmid et al., 2008). The continental Dacia Mega Unit is Europe-

derived, whereas the Tisza Mega Unit shows mixed European and Adriatic sedimentary affinities (e.g.

Csontos and Vörös, 2004; Haas and Péró, 2004; Iancu et al., 2005). Both Mega-Units comprise Variscan-

metamorphosed basement with Neoproterozoic crustal components and Late Paleozoic to Mesozoic cover

sediments (Pana et al., 2002; Balintoni et al., 2009; Balintoni et al., 2010). North Apuseni Mountains

comprise the Bihor Unit, which outcrops on large surfaces and the Codru Nappe System both belonging to

Tisza Mega Unit and Biharia Nappe System which belongs to Dacia tectonic Mega-Unit. Reiser et al. (2016)

emphasizes an important aspect of the Apuseni Mountains: existence within these mountains of an exposed

Figure 3.1 Geological setting of the Apuseni Mts (grey). The Moesian platform and the European foreland are

forming the pre-Alpine continental basement. Dark grey (within the Apuseni Mts) shows the suture between

the two microplates Tisia and Dacia. The dashed line is the prolongation of the suture in the Transylvanian

basin, covered by Neogene sediments, Schuller (2004)


Figure 3.2 Correlation between Mega-Units and structural units of the Apuseni Mts. Reproduced from

Merten et al., 2011.

contact between the Tisza and Dacia Mega-Units (Sǎndulescu 1994; Haas and Péró 2004; Csontos and Vörös

2004; Schmid et al. 2008; Kounov and Schmid 2013). Biogeographic data (e.g. Vörös 1977, 1993) indicate a

neighbouring position of the Tisza and Dacia Mega-Units along the European continental margin during the

Triassic and Early Jurassic (Figure 3.1 a). The Apuseni Mts have been formed during Cretaceous times as a

result of the convergence and collision of the two microplates Tisia and Dacia (Figure 3.1 b). The suture

within the newly created Tisia-Dacia block crops out in the south and southeast of the Apuseni Mts. Its

prolongation towards NE is covered by Neogene sediments of the Transylvanian basin. However, its

existence is known from geophysical data.

From the Middle Jurassic, onwards, both units were separated from Europe. Palaeomagnetic data show a

common apparent polar wander (APW) path for the European plate and the Tisza Mega-Unit up into the

Cretaceous, 130 Ma ago (Hauterivian/ Barremian; Márton 2000). Between Campanian and mid-Miocene

times, northward displacement and clockwise rotation by some 80°–90° affected both Tisza and Dacia Mega-

Units (e.g. Pătrascu et al. 1990, 1994; Márton et al. 2007; Panaiotu and Panaiotu 2010).

A brief chronology of major geological events in North Apuseni Mountains, from oldest to youngest, includes:


1 - Formation of various basement tectonic units, made up of Early Proterozoic metamorphic rocks (mostly

from high-grade metamorphic sequences) and associated granites (Late Cambrian ~502–490 Ma, Middle to

Late Devonian ~372–364 Ma and Early Permian ~278–264 Ma), with a Permo-Mesozoic sedimentary and

volcanic cover (e.g., Stan, 1987; Dallmeyer et al., 1999, Pana et al., 2002a).

2 - The delineation of system of nappes (Bihor, Codru, Highis-Drocea, Biharia, Baia de Aries), named the

Inner Dacides (Sandulescu, 1984), which have been juxtaposed during Late Paleozoic (Variscan) orogenic

activity (when they recorded three distinct tectonic phases at mid-crustal levels)

3 - Crustal shortening within Alpine tectonic activity during the Turonian

4 - Intra‐Turonian (‘Mediterranean’) westward back‐vergent thrusting, creating the retro‐vergent side of the

orogen in a series of four main nappe units: Mecsek, Bihor, Codru and Biharia (e.g., Săndulescu, 1984;

Balintoni, 1994; Haas and Péró, 2004; Schmid et al., 2008).

5 - Deposition of formations within Gosau-type basins during the Senonian.

6 - According to S. Merten et al. (2011), citing Bleahu et al., 1981; Balintoni, 1994; Willingshofer et al., 1999;

Schuller, 2004, etc, the Apuseni Mountains and the neighbouring Transylvanian Basin experienced

alternative deformation processes, as follows:

o Late Cretaceous (late Turonian–early Campanian) extension. Gradual subsidence and deepening of

sedimentary facies is recorded by the post‐collisional covers of ‘Gosau’ type, associated with the

contemporaneous formation of small grabens were mentioned.

o Compression, recognized at the scale of the entire Romanian Carpathians, resumed during the late

Senonian (late Campanian– Maastrichtian) ‘Laramian’ phase. Deformation generated structures

which change strike from low‐angle E‐W, trending nappe contacts with top‐N vergence in the

Southern Apuseni Mountains to N‐S high‐angle reverse faults with large along‐strike offset

components at the eastern margin of the Apuseni Mountains (Figures 3.3 b and c).

o The latest Cretaceous – earliest Palaeogene post‐collisional sedimentation spans several sequences

of mainly continental terrigenous sedimentation.

7 - Deformation was coeval with and followed by latest Cretaceous intrusive and extrusive (sub‐) volcanic

Banatitic magmatism. The magmatic rocks are mostly extrusive (sub‐) volcanic in the southern part of the

Apuseni Mountains (Seghedi, 2004) and mostly intrusive in the northern part, except for part of the Vlădeasa

volcano plutonic complex (Figure 3.3 c).

o Re‐Os ages of Banatitic magmatic activity range between 88–81 Ma for the South Carpathians to 84–

72 Ma for the Apuseni‐Banat area (Zimmerman et al., 2008).

o For the Apuseni Mountains, K‐Ar and 40Ar/39Ar ages indicate latest Cretaceous–Eocene cooling of the

Banatites (Bleahu et al., 1981; Wiesinger et al., 2005).

o Based on 40Ar/39Ar amphibole and biotite ages ranging between 89 Ma in the South Carpathians to

61 Ma in the Apuseni Mountains, Wiesinger et al. (2005) suggested three consecutive magmatic

events: Turonian–Santonian, Campanian and Maastrichtian. The bulk of the Paleocene – Eocene

ages are derived from older K‐Ar measurements (Bleahu et al., 1981) and represent cooling ages.


Figure 3.3 Cross–section illustrating deformation and magmatism processes in the Apuseni Mts (Marten et

al, 2011)


3.2 Structural settings of North Apuseni Mountains

The Apuseni Mountains (Figure 3.4) in Romania take a central position in the Alpine – Balkan – Carpathian –

Dinaride realm (Mitchell 1996; Janković 1997) between the Pannonian basin in the West and the

Transylvanian basin in the East. From the morphologic point of view, the North Apuseni Mts (Northern

Figure 3.4 Simplified Alpine structure of the Apuseni Mountains from Ionescu et al. (2009) compiled by C.

Balica from papers by Ianovici et al. (1976), Bleahu et al. (1981), Săndulescu (1984), Kräutner (1996), and

Balintoni & Puște (2002). Black square – North Apuseni Mts; blue square – Bihor Mts.


Apusenides or Internal Dacides) consist of Bihor Mountains together with Highiș, Codru, Pădurea Craiului,

Gilău, Mezeș, and Plopiș Mts (see Figure 3.4). The architecture of the Apuseni Mts contains, as the

structurally deepest unit, the “Bihor Autochthonous Unit” or the “Bihor Unit”. This unit has a regional extent

and has a relative autochthonous position in respect to the higher nappe systems, covering a good part of

the northern segment of the Apuseni Mts. The structurally higher units can be grouped, according to their

origin and lithological content, in two nappe systems, thrust on top of the “Bihor Autochthonous Unit”:

- the deeper Codru Nappe system

- and the tectonically higher Biharia Nappe system.

Figure 3.5 Tectonic map of Apuseni Mountains. Abbreviations for North Apuseni Mountains: B.A.- Baia de

Arieș Nappe; M.L.- Muncel–Lupșa Nappe; Bi – Biharia Nappe; H.P. – Highiș-Poiana Nappe; A – Arieșeni

Nappe; Ve – Vetre Nappe; C.U. – Colești-Următ Nappe; Va – Vașcău Nappe; Mom – Moma Nappe; D.B. –

Dieva-Bătrînescu Nappe; F.G. – Finiș-Ferice-Gîrda Nappe; V – Vălani Nappe; A.B.- Bihor Autochtonous

3.2.1 Study case perimeter

This paper focuses two main structural main units, which are relevant for our study purposes: Bihor

Mountains and Beiuș Depression, which are part of North Apuseni Mts. Beside a general description of North

Apuseni Mts emphasis of some specific features of these units is necessary (Figure 3.6).


3.2.1.1 Bihor Mountains

The Bihor Mountains consist of three distinct units, which are well defined both in their topography and their

geological framework: Vlădeasa, Bihor and Biharia Mountains. All three have a pre-Alpine basement,

consisting of crystalline schists and granitoids, generated in the pre-Bailkalian, Bailkalian, and Hercynian

cycles and covered by a generally unmetamorphosed Permian molasse.

The basement is covered by Triassic to Lower Cretaceous carbonate and terrigenous sediments devoid of

initial magmatism products. The Austrian orogeny generated the Northern Apusenides nappe structure

consisting of three tectonic units.

The Bihor Unit, built up by pre-Baikalian metamorphic rocks, and their Mesozoic cover;

The Codru Nappe System, consisting of following nappes: Vălani Nappe, Finiş-Ferice-Gârda Nappe

and Moma-Arieşeni Nappe, Dieva-Bătrânescu Nappe, Următ Nappe and Moma-Arieşeni Nappe,

composed of Paleozoic and Mesozoic formations;

The Upper Nappe System (The Biharia and Muncel Nappes), built up of deposits related to Baikalian

and Hercynian tectogenetic cycles.

Bihor Unit (Autochthonous)

For the lowermost, Bihor Unit, the crystalline basement consists of the medium-grade Somes Series

(micaschists, amphibolites, leptynites) and the retrogressive Arada Series (chlorite-sericite-albite schists,

metarhyolites), both intruded by the Muntele Mare granitic massif. The ages of the metamorphism and of

the intrusion are Paleozoic.

The sedimentary sequence of the Bihor Unit includes, (besides very scarce Permian rocks) Triassic, Jurassic

and pre-Senonian Cretaceous formations. The following specific lithostratigraphic features must be

underlined:

development of a carbonate platform series from the Upper Werfenian to the base of the Carnian;

absence of the major part of the Upper Triassic;

Gresten paralic facies of the Lower Jurassic;

marine sequence of the Middle Jurassic and of the base of the Upper Jurassic;

development of a carbonatic platform in the Kimmeridgian and Tithonian;

the uplifted and subaerially exposed Tithonian limestones were covered by residual bauxite deposits

of Lower Cretacoeous;

calcareous neritic lithofacies of the Barremian and Aptian, passing into a marly sedimentation which

continues in the Turonian.

The Bihor Unit corresponds to the Villány Unit in southern Hungary and to the Tatride units in the Slovakian

Carpathians, and is probably overthrust northwards onto the Tethysian Suture.

Codru Nappe System

A number of nappes are overthrust on the Bihor Unit (Figure 3.5).

The Vălani Nappe is the lowest unit, thrust over the Bihor Autochtonous, and consists of Permian to Lower

Aptian sequences. The Finiș-Ferice-Gârda Nappe, has a metamorphic basement consisting of the Codru


Figure 3.6 Study case perimeter map – edited in GIS by Gabriel Preda, after Geological map of Romania.

Scale: 1:200,000. (Source: Geological and Geophysical Institute, authors: Bleahu, Savu, Borcoș for Brad Sheet

and M.Lupu, Borcoș, Lupu, Bitoianu for Simleul Silvaniei Sheet) (Legend on next page)


Figure 3.6 (cont.): Legend of Study case perimeter

granitoids and migmatites, which are the oldest basic intrusions, pre-Hercynian iage (400 m. a.), according to

Dallmeyer et al. (1994). As specific lithostratigraphic features, the following are to be mentioned:


large development of Permian felsic ignimbritic volcanism;

complete development of the Triassic sequence, with Carpathian Keuper and Kössen facies in the

Late and latest Triassic;

marine, marly-calcareous facies of the Lower Jurassic;

development of a flysch-type sequence in the Tithonian-Neocomian.

The Dieva-Bătrânescu Nappe is characterized by:

a complex magmatism in the Permian, with mafic rocks intercalated between two rhyolitic

sequences;

development of Reifling and Dachstein facies (until the Upper Norian);

missing Jurassic rocks.

The Următ Nappe is developed similarly to the Finiș Nappe, in wildflysch type facies, with variations at the

level of the Jurassic.

The Moma-Arieșeni Nappe overlies all the other units, including the Bihor Unit. The oldest formations of this

nappe consist of the Lower Carboniferous Arieșeni Series (greenschists intruded by doleritic veins). The

Upper Carboniferous and Permian molassic formations of reddish colour are well developped, including

acidic eruptive products. The Middle and Upper Triassic formations, up to Rhaetian, occur in calcareous

facies. The highest nappes of the Codru System display Triassic sequences in Hallstatt and Dachstein facies.

Biharia Nappe System

This group of nappes consists essentially of pre-Carboniferous metamorphic formations (Biharia Series:

orthoamphibolites, chlorite-schists with albite porphyroblasts; Muncel Series: sericite schists, mylonitic

granites, metarhyolites) overlain by the metaconglomeratic Upper Carboniferous Păiușeni Series.

Post-tectogenetic cover

The described nappes, building up the Internal Dacides (Northern Apusenides), characterized by a Turonian

main tectogenesis (similarly to the Slovak Central Carpathians or to the Eastern Alps), are post-erosionally

overlain by the Senonian Gosau Formation. The reef facies of the Senonian consists of coralian limestones,

while the volcanic-sedimentary formation includes alternating volcanic ashes, tuffs, tuffites, sandstones,

micro-conglomerates, breccia and conglomerates with terrigenous-volcanic matrix (Mantea, 1985).

The post-tectonic subduction magmatism is represented by banatites.

Neogene formations

On the western rim of the Bihor Mountains, Pannonian s.s. (Malvensian) deposits, consisting of clays with

coal, sand and gravel interbeds of the Beiuș Neogene basin infill are outcropping. In the close neighborhood

of the mountains coarse deposits prevail, that are substituted gradually by pelitic facies towards the middle

of the Beiuș Basin.

Quaternary formations consist of sands, gravel, boulders, and, subordinately, clays. They occur in the

terraces of rivers (Crișu Pietros) and along smaller streams.

Late Cretaceous, Banatitic magmatism

In the Bihor Mountains, an outstanding example of Late Cretaceous magmatism is the volcano-plutonic

Vlădeasa Massif. Here a volcano-sedimentary formation is overlain by andesites, dacites and ignimbritic

rhyolites; all crossed by minor quartz-dioritic and monzogranitic intrusions. The rhyolitic rocks are of

different facies, ranging from massive to vitrophyres, as a function of the place where the rhyolitic magma

solidification has occured (i.e. under the Senonian sedimentary cover or subaerially). In the evolution of the


magmatic activity of this area there have been two outstanding events, namely the emplacement of the

ignimbritic rhyolites formation and the set up of the intrusive bodies.

Southwards, a granodioritic-granitic batholith crops out and is also associated with andesitic and rhyolitic

minor intrusions. The batholith body, which is of hypoabyssal origin, extends within Bihor Mountains, both at

the surface and in the underground, up to the Galbena Fault. At the surface, in the Pietroasa – Aleului valley

area, and further north, up to Budureasa, granodiorites largely outcrop. Associated with this banatitic

intrusion, apophyses and bodies of andesitic or basaltic composition have been documented, especially in

the upper reaches of Crișu Bãița, along the Hoanca Moțului, Corlatu and Fleșcuța valleys, as well as in the

Valea Seacã catchment area. The intrusion of the banatites has produced contact metamorphic phenomena

affecting the sedimentary deposits traversed. At the contact of the banatites with limestones or marbles

various types of calcic skarns have been formed, while at the contact with the terrigenous, granular and

pelitic rocks, hornfels, garnet skarns, etc. resulted.

3.2.1.2 Beiuș Basin

The Beiuș Basin is a post-tectonic intramontane basin, infilled with Miocene, Pannonian, and Quaternary

deposits overlying a heterogeneous basement of Mesozoic, Paleozoic and Proteozoic deposits of the

Northern Apuseni Mountains. Around and inside the Beiuș Basin following tectonic units have been

reported:

The Bihor Unit is represented in the northern and north–eastern part of the basin by Upper Jurassic and

Cretaceous formations; up to Albian carbonate platform deposits prevail, being substituted (toward the

upper part of the Cretaceous, including the Lower Turonian) by shallow water, siliciclastic deposits.

The Codru Nappe System - Bihor Unit is overlain by the Vălani Nappe, the lowest unit of the Codru Nappe

System, occurring along the northern margin of the Beiuş Basin. Other tectonic units of the Codru Nappe

System are the Vălani Nappe, the Finiş Nappe, and the Dieva Nappe.

The post-tectonic cover formed of Senonian formations in Gosau facies, mask the thrust contacts of the

Codru Nappes, especially in Bihor Mts.

The Neogene deposits are represented by Badenian, Sarmatian, Pannonian s.s. (Malvensian) and Pontian

formations (Marinescu, Bordea et al, 1995). The Beiuș Basin represents an eastern gulf of the Pannonian

Basin. The filling of this basin consists of Neogene deposits in Pannonian facies (Bordea et Mantea, 1999).

The total thickness of these deposits does not exceed 1200 m.

The Quaternary cover consists of widespread, alluvial deposits along the main streams and other genetic

types of subaerial deposits.

In the central–eastern part of the Beiuș Basin, east of the locality Pomezeu, between Holod and Roșia

valleys, banatitic intrusive rocks (Paleocene porphyric granodiorites) are cropping out. They form a 5 km long

lineament, with a NW–SE trend, parallel with the Dobreşti Fault (Bordea et Mantea, 1999).

The tectonics of Beiuş Basin based on geological and geophysical data

Bordea et Mantea (1999) identified a near-parallel pattern of steep, straight faults oriented along the Beiuş

Basin. Some of these were intruded by banatite rocks, as in the case of the Galbena Fault, in the eastern

margin of the basin. These deep, normal faults were generated in the upper crust by a tensional stress

induced by thermal doming above a large banatite body and were infilled as a consequence of the vertical

stress exerted by the rising of molten magma.


Aeromagnetic, surface magnetic, gravimetric and seismic (refraction methods) data were combined for

obtaining an image of the deep structure of the Beiuş Basin (Dinu et al., 1991). Dinu et al (1991) presented

an isobath map at the base of the Neogene fill of the Beiuş Basin. Base on this map Dinu et al concluded that

the structure of the Beiuş Basin is of collapsed basin type, made of down-thrown blocks along steep-angle

faults. Faulting caused topography with uplifted and dropped sectors trending NW-SE.

From the aeromagnetic anomalies two intrusive magnetic bodies have been identified (Figure 3.7).

Aeromagnetic data show an anomalous zone with two maxima, of the same amplitude and morphology,

situated in the center of the basin (Dinu et al., 1991). The anomalies are supposed to be the expression of

two deep seated vaulted magmatic bodies. The top of one of these bodies is at 1.7 to 1.8 Km from surface

(in the Lupoaia zone) while the top of the second lies at 1.2-1.4 Km beneath the surface (halfway between

Rotăreşti and Albeşti). The lateral extent of these anomalies was estimated to reach about 4 km at 4 km

beneath the surface, suggesting the existence of a large magmatic body buried in the depth.

Figure 3.7 Map of vertical gradient of magnetic anomaly (TZ) from Beiuș Basin


3.2.2 How Bihor Mountains can positively contribute to the aims of CHPM2030

Extensive database of reports acquired especially during 1960–1995.

Good understanding of the geological evolution of the region.

Continuous digital geological mapping at 1:50,000 scale.

The geological maps, scale 1: 200,000, are correlated to structural wells.

The geological maps, scale 1: 200,000, are correlated to geophysical investigations of low resolution.

3.2.3 Limitations in our current understanding of Bihor Mountains

The majority of the primary data that exists is related to the shallow sub-surface (<1,000 m,and

often <200 m).

There has also been no detailed deep geophysical investigation. As a consequence, this presents

uncertainty in terms of extrapolating information and data at surface to any significant depth.


Many authors’ analyses integrate Northern Apuseni Mountains Alpine magmatism within a broader context,

defined by the term Banatitic Magmatic and Metallogenic Belt – BMMB –, which represents a series of

discontinuous magmatic and metallogenic occurrences of Upper Cretaceous age, which are discordant in

respect to Mid-Cretaceous nappe structures (Cioflica & Vlad, 1973; Ciobanu et al., 2002).

The subvolcanic /plutonic rocks belonging to the BMMB are known under the collective name of “banatites”,

a term coined by Von Cotta (1864) who described a suite of cogenetic magmatic rocks occurring as either

shallow intrusions or subvolcanic bodies, younger than Jurassic and Cretaceous sedimentary formations.

Ever since this first description, the name “banatites” has reflected their locus tipicus, that is, Banat and

Timok region, covering parts of the south-western Romania and north-eastern Serbia. During the last few

decades, the BMMB has drawn considerable interest in petrology, age, and structural-tectonic significance

and in the contained skarn, porphyry-copper and hydrothermal ore deposits, with a vast amount of literature

published to date (Ilinca, 2012).

In Euroe the BMMB is exposed over approximately 900 km in length and around 30 to 70 km in width. It has

a north-east to south-west trend over Apuseni Mts and Southern Carpathians, it aligns to a north - south

direction over eastern Serbia (Timok and Ridanji-Krepoljin zones), and bends widely to the east, through the

Srednogorie area, reaching the shores of the Black Sea (Figure 3.8).

The occurrences of the BMMB in Romania are in Apuseni Mountains where banatites are found both as

volcanics in Late Cretaceous Gosau-type basins (e.g., Vlădeasa, Corniţel-Borod, Gilău-Iara, Sălciua-Ocoliş,

Vidra, Găina, Roşia) and as dyke swarms or major intrusions, cross-cutting these volcanics or any older

formations or tectonic planes (e.g., Gilău, Budureasa, Pietroasa, Băişoara, Valea Seacă, Băiţa Bihor, Brusturi,

Căzăneşti, Măgureaua Vaţei) – Ilinca, 2012.

The distribution area of banatitic magmatites in Northern Apuseni Mts is a complex geostructural

assemblage represented by rocks emplaced previously to banatites, (metamorphic and/or sedimentary and

igneous rocks), that are overlain by the Upper Cretaceous sedimentary cover consisting of carbonate and

detrital rocks. The banatitic magmatites pierce or lie over these formations, generating magmatic contact

phenomena or mineralisations, and are transgressively overlain by the Tertiary sedimentary rocks of the


Transylvanian Basin. The metalogenesis of Bihor Mountains is closely linked to the evolution of banatitic

magmatism in the North Apuseni Mountains (Figure 3.9).

Figure 3.8 Extension of the Banatitic Magmatic and Metallogenic Belt. Romania, Eastern Serbia and Bulgaria

(with dark gray in the inset and with heavy outline in the map). Simplified after Cioflica and Vlad (1973)

The data on evolution of banatitic magmatism and the metalogenesis of Northern Apuseni Mountains, were

adapted from Ștefan et al, (1992), which synthetised the works conducted in the region before 1989 by:

Mureșan, 1971; Lazăr et al., 1972; Istrate, Bratosin, 1976; Istrate, 1978; Ştefan, 1980; Udubașa et al., 1980;

Istrate, Udubașa, 1981; Ştefan el. al., 1985, 1986, 1988; Ştefan et al., 1989, unpublished report.

3.3.1 Evolution of banatitic magmatism of Bihor Mountains

The banatitic calcalkaline magmatism (Post-Lower Masstrichtian-Paleogene) which is widely developed in the

Bihor Mountains, was emplaced within two important cycles unequally represented from one zone to

another.

The first cycle is characterized by lava flows of quartziferous andesites (bearing pyroxenes and hornblende or

only hornblende to which sometimes adds biotite) (Vlădeasa) sometimes accompanied by pyroclastic rocks

(Vlădeasa); simultaneously superficial subvolcanic bodies have been emplaced (Vlădeasa, Bihor).

The typical development area of the first cycle volcanism – the Vlădeasa Mts – contains the greatest volume

of rhyolites forming the volcano-plutonic massif of Vlădeasa (Giușcă et al., 1969). The rocks of the Vlădeasa

main eruptive body cut and include andesites, dacites and two older rhyolite rock types producing contact

breccias with them. Although the Vlădeasa rhyolites represent subvolcanic bodies, they exhibit ignimbrite

features (Ștefan, 1980).


Figure 3.9 Map showing the distribution of the banatites in the Apuseni Mts (Ștefan el al. 1992, modified

after Borcoș, with aditional data). The sites are: I-Vlădeasa; II-Budureasa-Pietroasa; III-Bihor (V. Fagului, V.

Seacă); III’-South Bihor; IV-Gilău; V-Trascău; VI-Magureaua Vaței; VII – Mezeș, Chioarului Valley

The volcanic and the near-surface subvolcanic rocks belonging to the first cycle, rarely produce contact

phenomena. However, andalusite hornfelses formed at the expense of some metamorphic rocks were

reported in North Vlădeasa. In addition, all the xenoliths are nearly completely digested and transformed to

hornfelses reaching the pyroxene facies.

The products of hydrometasomatic metamorphism are rather abundant in the rhyolites of Vlădeasa main

body; epidote and sometimes zeolites are very well represented. Generally, the banatitic volcanic rocks and

especially rhyolites are autometamorphically changed or are transformed by a late contribution of

hydrothermal solutions; excepting pyrite, which is very rare, they are not accompanied by metalliferous

minerals.

Within the second main cycle bodies of intrusive hypabyssal origin, or intrusive plutonic bodies have been

emplaced (Proca, Proca, 1972; Cioflica et al., 1982). Late alkaline vein differentiation products of

granodiorite-granitic magma were reported too. This stage of magmatic banatitic activity in the Bihor Mts

ends with dykes of basic rocks (very abundant in Bihor).


Banatitic magmatism of the second cycle begins with quartziferous diorites and their porphyritic varieties

(porphyritic micro diorites, diorite porphyries - quartziferous andesites), which, in Bihor, cross the rhyolites

of the first cycle (Jude, Ștefan, 1967). In the southern part of the Bihor Mts at Hălmăgel and Obârșa,

quartziferous diorites are crossed by granodiorite-granites, and at Stânișoara, porphyritic rocks of diorites

composition in the subvolcanic bodies are thermally changed into the contact aureole of a granodioritic-

granitic body. At Băișoara, such rocks of diorite composition constitute the marginal facies of the rocks

bodies of granodioritic composition.

In Pietroasa, Budureasa and Western Vlădeasa massif, quartz-dioritic rocks occur either as some

independent bodies or at the periphery of granodiorite – granitic – monzodioritic rocks; in fact, they are

included here as xenoliths. Porphyritic micro diorites are also met in the northern extremity of eastern

Vlădeasa eruptive massif, north of Crișul Repede River.

Skarns often accompanied by magnetite concentration occur almost everywhere at the contact between

dioritic and carbonate rocks, sometime base metal sulphides associate with the skarns (Figure 3.9). So, at

Măgureaua Vaței skarns of a very rich paragenesis (gehlenite, spurrite, tilleyite, garnets, pyroxenes,

wollastonite, and vesuvianite) are associated to Fe ± Ba metasomatic mineralizations in the western

extremity of quartz-mondozodioritic body and sulphide veins in the eastern extremity on the magmatic

body, where granodiorite-granites prevail. On Martin hill at Sârbi-Hălmăgel, in the aureola of dioritic body,

which is crossed by granodiorites, iron oxides and sulphide mineralizations occur. Magnetite associated with

banatitic magmatites are also found at the spring of Arieșul Mic, Valea Seacă and Budureasa; at Valea Seacă

and Budureasa, sulphide mineralizations overlie this kind of mineralizations.

Granodiorite-granites to which the main sulphide mineralizations are genetically connected constitute main

mass of banatitic bodies in the Apuseni Mts; although they crop out on small areas, their development in the

depth was emphasized (in the Bihor Mts).

Around big bodies of granodiorite-granitic composition, phenomena of thermal metamorphism are

reported. Their extention is arround the pluton is 1500 m as in the Bihor Mts (Cioflică et al., 1974). Although

products of thermal metamorphism are wideley spread in the Bihor, excepting some intensely hormfelsed

xenoliths (where sillimanite prevails) intensity of thermal matamorphism reached only the facies of

hornblende hornfelses.

Under geologically favorable conditions, i.e. in the contact aureola of the granodiorite-granites plutons, Fe,

B, Bi, Mo bearing skarns have been formed, locally overlapped by sulphide mineralizations, sometimes

independently developed, such as the vein occurrences with Cu, Zn and Pb sulphides at Valea Seacă, Valea

Mare-Budureasa etc.

The second cycle of banatitic magmatism ends with alkaline differentiates rich in SiO2 and K2O; they form

veins of aplites, micro granitic and/or micropegmatitic rhyolites, porphyritic micro granites etc. In the Bihor

and Budureasa-Vlădeasa Mts such rocks form NNW-SSE trending dykes with extension varying between

hundreds of meters to some (few) kilometers. Such rocks did not generate products of thermal

metamorphism to be significant and are not accompanied by mineralizations (Istrate, Udubașa, 1981).

After the consolidation of the granodiorite-granitic magma, basaltic andesites, basalts and lamprophyres

have been emplaced on deep fractures; they come from a different, deeper magmatic source. These basic

rocks are nearly synchronous with the later differentiates of the granodiorite-granitic magma (as in the Gilău

Mts) or they are much later emplaced simultaneously with the circulating hydrometasomatic solutions

associated to granodiorite-granitic plutons, as in Bihor Mts. The lamprophyre dykes, typically developed in


the Bihor Mts have a similar trend, i.e. NNW-SSE, to that of differentiation products of the granodiorite-

granitic magma (rich in SiO2 and K2O); the former cut the alkaline differentiates.

3.3.2 Banatitic metallogenesis in Apuseni Mountains

Occurrences and ore deposits which are genetically associated to banatites in the Apuseni Mts belong to

(Laramian) banatitic metallogenetic belt.

The Apuseni Mts banatitic metallogenesis is centred on the Bihor Mts zone, with a maximum complexity in

the Băița Bihor ore deposit. An obvious horizontal zoning appears around this important ore deposit (Figure

3.10). The internal zone contains Co, Ni, Mo, Fe, Bi, Ag, Au mineralizations, the most typical being the Gruiul

Dunii ore deposit, including the whole zone between the spring area of the Crișul Negru, Arieșul Mic and

Arieșul Mare rivers. It follows a discontinuous zone with iron oxides (magnetite, hematite) and base metal

sulphides; the typical ore deposit belonging to this zone is that at Brusturi (Dolii Hill). The external zone

contains Pb-Zn and pyrite ores. All the zones may contain gold occurrences but they are typical of the

external zone.

The regional zoning is however, incompletely known and the zones show uncertain boundaries towards east.

Therefore, the metallogenesis cannot be ascribed to a single magmatic body but to several ones with

simultaneous mineralizing activity. The most important is the Central Bihor pluton, in whose apical zone

there are a lot of mineralized structures with skarns and subsequent polymetallic mineralizations.

Periplutonic zoning of the Bihor Mts mineralizations was established both by means of metallic minerals

associations and geochemical data (Lazăr et al., 1982; Cioflica et al., 1982). Northwards, the superficial

pluton (Hochpluton) Budureasa-Pietroasa-Vlădeasa is accompanied by weaker mineralizations. East of the

Apuseni Mts, a similar pluton, the Gilău-Băișoara zone, had a metallogenetic iron-polymetallic activity at the

end of its evolution.

The most important types of mineralizations are the ones associated to skarns (especially B, Fe, Bi, Mo, W

and Cu concentrations) and hydrothermal concentrations, in which impregnation and substitution processes

played a subordinated part. Hydrothermal mineralizations are much more diversified in comparison with

pyrometasomatic ones, which they often overlie.

Metallogenesis associated to banatites in the Apuseni Mts has distinct features in comparison with that from

Banat. Firstly, in the Apuseni Mts skarns are not so developed; secondly magnetite mineralizations are only

locally developed (Băișoara zone); thirdly the main metals in the ore deposits are more diversified than in

Banat; their major geochemical spectrum includes Bi, Mo, Pb, Zn, Cu, B, Fe, W, Co, Ni, As etc. while in Banat,

where according to the importance there is another series of metals: Cu, Fe, Bi, Zn, Pb, W, Mo, Co.

In the Apuseni Mts, representative bodies of skarns of very different forms and sizes are known in the Bihor-

Budureasa, Gilău massifs and Măgureaua Vaței (Figure 3.10). Skarns generation was controlled both by the

circulation ways occurred near the banatitic plutons and by the paleosome nature. The limestones and

dolomites both from the crystalline series and Mesozoic deposits prove to be very favorable to the

substitution processes.

Regarding the types of skarns which occur, we remark on one side, prevailing infiltration skarns in relation

with the contact ones, on the other side, prevailing apocarbonatic skarns in relation with aposilicate ones;

calcic skarns are more developed than magnesian ones.

Mineralizations of iron oxides occur in the Apuseni Mts, especially in Băișoara – Mașca -Cacova Ierii (Lazăr,

Întorsureanu, 1982), at Măgureaua Vaței, Martin Hill (Hălmăgel), spring of Arieșul Mic end Valea Mare


Figure 3.10 Regional distribution of the mineralization types in the Apuseni Mountains. Legends: 1, Baritine

occurrences; 2, Brucite occurrences; 3, Pyrite occurrences with, or without gold; 4, polymetalic occurrences

(Cu, Pb, Zn); 5, occurrences with Co, Ni, As, Bi, Ag ore; 6, Bi, Mo, W, B, Cu, Pb, Zn occurrences; 7, Fe with, or

without Cu occurrences; 8, minor elements characteristic (downwards) in pyrite, spalerite, galena; 9,

outcrop, areas with hollocrystalline, equigranular rocks; 10, zones contours; 11, geophysical anomalies.

(Stefan et al. 1986).

(Budureasa). They associate spatially and maybe genetically either to some intrusive dioritic or monzodioritic

bodies or to some basic envelopes of some granodioritic bodies. To granodiorite – granitic plutons (ex. Băița

- Dedeș valley pluton, Bihor) are associated obviously polymetallic mineralizations, which consists mainly of

sulphides and sulphosalts, more rarely sulphoarsenided and arssenides of Fe, Ni and Co.

Hydrothermal mineralizations are widely spread in the Bihor massif (Râul Mic, Brusturi-Luncșoara, Valea

Vacii, Șipot brook, Valea Seacă etc.), as well as in Budureasa, Vlădeasa massifs, at Julești-Valea Fagului, in

Plopiș Mts (at Bucea-Cornițel), in Gilău Mts (Valea Lita, Băișoara), on the Birtinului Valley and at Căzănești

and Almașul Mic, in the Metaliferi Mts too.

The hydrothermal minerals are frequently spatially associated with skarn and high temperature minerals

(such as magnetite, ludwigite, ilvaite, scheelite, molybdenite, bismuthite, pyrhotite) and generally succeed


the skarn stage of post magmatic mineral formation. The hydrothermal ore minerals build up mainly veins

and hydrometasomatic bodies; locally there are impregnation bodies, stock works, or simple nests.

The ore veins are related to breccias zones or along fractures and their trend (especially in the Bihor Mts) is

mostly NNW-SSE, which is the same as the trend of the lamprophyres dykes closing the banatitic magmatic

activity. The size of the ore veins is quite variable: hundreds of meters in length and some few meters in

width. Their vertical extension varies from some tens of meters (Julești-Valea Fagului) to 100-200 m (Almașul

Mic, Bucea, Cornițel) and, more rarely 300–500 m (Băița Bihorului, Brusturi-Luncșoara).

Some ore deposits have an obvious vertical zoning. A characteristic example is Brusturi-Luncșoara ore

deposit, which was opened by means of mining works at about 350 m depth. At the upper levels, there is a

lead-zinc mineralization, while at the lower levels; cupriferous character of the mineralization becomes move

obvious. This modification of Cu/Pb+Zn ratio is accompanied by an increasing amount of skarn and iron

oxides minerals.

Impregnation and/orsubstitution bodies can be sometimes lenticularly developed, being very long and

flattened. They are often parallely oriented with the regional system of fractures (SW-SE), rarely about E-W

(ex. Bucea-Cornițel, acc. to Berbeleac et al., 1982).

Processes of metasomatic metamorphism which influenced both crystalline formations and Pre-Paleogene

sedimentary rocks and banatites are very widely spread; therefore, their products are everywhere found.

The aureola of hydreothermal metamophism is much more extended than thermal and / or

pyrometasomatic metamorphism, which it some time overlies.

The contact metamorphic aureola of the granodiorite-granitic pluton in the Bihor massif has the greatest

extension; on the vertical scale, it reaches 2000 m or more (Lazăr et al., 1982). The alteration processes are

described in numerous papers, e.g. (Gherasi, 1969; Cioflica et al., 1974, 1982; Giușcă et al., 1976; Ionescu,

Berbeleac, 1971; Lazăr et al., 1982) and typical minerals of K-feldspar-, propylitic-, sericitic- and argilitic

alteration zones have been depicted; some alteration minerals occur in vugs, e.g. quartz, carbonates,

feldspars, epidote, chlorite, clay minerals, zeolites, accompanying the ore minerals.

3.3.3 Chemical composition and origin of banatites

Stefan et al., 1992, realized a geochemical study of banatitic magmatites from Northern Apuseni Mts, based

on both new analyses (chemical, emission and gamma-spectrometry, X-ray fluorescence, neutron-activation

for REE) and published data; some isotope data analyses (87Sr/86Sr and K-Ar) were included.

The conclusions of this study are, as follows:

The evolution of banatitic magmatism implies two cycles: a first cycle, marked by the emplacement

or volcanics (andsites, dacites and rhyolites) and a second cycle, characterized by the emplacement

of plutonic and hypabyssal rocks of dioritic, granodioritic and granitic composition, ending with their

alkaline differentiates dykes. Basaltic andesites, basalts and lamprophyres dykes, of different origin,

partly contemporaneous with the mentioned alkaline differentiates end the magmatic activity in the

Northern Apuseni Mts.

The major and minor contents and distribution, REE inclusively, compared to published data and

graphically represented on diagrams, show the consanguinity of volcanics and plutonic and

hypabyssal magmatites, better arguing the concept concerning the evolution of banatitic

magmatism in the Northern Apuseni Mts.


According to 87Sr/86Sr isotope data and other geochemical data graphically represented, one

accounts for the genesis of calc-alkaline magmas by oceanic crust subduction, followed by complex

evolution of melt, within several magmatic chambers, associated with assimilation and

differentiation processes.

The pointing out of two and respectively three zircon populations, which show different origins,

agree with the petrogenetic concept according to which the calc-alkaline melt, generated by oceanic

crust subduction, was contaminated with sialic matter during its ascension, the more obviously as

the contact with the sialic crust had longer existed.

An exhaustive description of the banatitic rocks from Bihor Mts, is found in a study by Stoicovici and

Selegean, 1970. Based on chemical composition, Niggli symbols, and QLM values, the authors realised

Niggli’s diagram for banatitic rocks, resulting the nature of magma generating the rocks from different

locations of Bihor Mountains. It resulted that in Bihor Mountains, there is an important post orogenic

magmatic activity, highlighted by outcropping of several intrusive bodies consisting of rock with generally

neutral composition (Găina-Luncşoara), slightly acid or acidic (V. Seacă – Stânişoara) and acid composition

(Pietroasa – Budureasa).

Along the principal direction of manifestation of banatitic magmatism of Bihor, which is SE-NW, there is a

gradual increase in the acidity of the rock, so that, within Budureasa area, the most acidic term of banatites

appears, whereas in the Găina-Luncşoara, the term most basic is in place.

The rocks that had been in contact with granodioritic magma and its apophyses, contaminating them, are

made up of different series of crystalline schist rocks, of Permian sediments who were developed up to the

springs of Galbena valley, and to Seaca valley. Best represented is the series of Mesozoic sedimentary rocks,

of limestone composition and subordinate clay, Mesozoic rocks reaching their maximum development from

V. Seacă until near the villages of Pietroasa and Budureasa.

These limestones with a regional development underwent a process of transformatin into marbles, and

cracking, and these Triassic (Anisian) marbles represent the rocks in which geothermal aquifer is hosted.

The most intense magmatism is localized along a SE-NW direction, which is the direction of the main regional

faults. But along this main direction, variations in the intensity of contact metamorphism of can be found.

This contact metamorphism is manifested by a halo of about 100 m around intrusive bodies in the northwest

region and by a halo of up to 1500 m the southeastern region.

Depending on the chemistry of the banatitic magma and depending on the specifics of surrounding rocks

various types of deposits were formed, like those of molybdenum, boron, polymetallic and gold-bearing

mineralized. Together they represent the important mineralised field of Bihor Mountains. These deposits are

usually localized within the cupola of the intrusive body (Bihor-Molybdenum) in its flanks (Brusturi-Dobrin) or

near the intrusive bodies that outcrop (Netiţei-Pietroasa).

In 2015 Jacqueline Vander Auwera et al, realized an extensive analysis of the origin and composition of the

Late Cretaceous igneous rocks of Romania (Apuseni Mountains and Banat). Based on new whole-rock major

and trace elements as well as 87Sr/86Sr and 143Nd/144Nd isotopic data of a suite of samples collected in the

Late Cretaceous volcanic and plutonic bodies of the Apuseni Mts (Romania) that belong to the Banatitic

Magmatic and Metallogenic Belt. Major and minor concentrations from the main deposits are given below:

Table 3.1 (next pages): Major and trace element concentrations in the Pietroasa, Budureasa, and Băița Bihor

(Bihor Mts) whole-rock samples


Peri-

meter

Băiţa

Bihor Pietroasa Budureasa

An

des

ite

Dac

ite

Dac

ite

Dac

ite

Dac

ite

Trac

hy-

dac

ite

Dac

ite

Trac

hy-

and

esit

e

Rh

yolit

e

Trac

hy-

and

esit

e

Bas

asal

tic

and

esit

e

SiO2 55.04 65.38 65.32 66.43 66.6 63.06 66.8 55.07 69.87 55.88 52.05

TiO2 1.08 0.6 0.49 0.62 0.6 0.92 0.62 1.16 0.42 1.29 1.47

Al2O3 15.33 15.09 14.93 15.39 14.98 15.93 15.31 18.61 13.97 19.15 18.16

Fe2O3 8.15 3.93 4.21 3.86 3.71 5.32 3.48 6.94 2.85 6.53 9.11

MnO 0.12 0.1 0.07 0.08 0.08 0.13 0.07 0.1 0.05 0.09 0.18

MgO 5.33 1.33 1.88 1.24 1.12 1.29 1.13 2.66 0.66 2.65 4

CaO 7.78 3.28 3.5 2.78 2.9 3.21 2.97 5.99 1.04 5.28 7.61

Na2O 1.03 3.66 3.29 3.84 3.69 4.46 3.79 4.08 3.16 4.09 3.27

K2O 3.19 3.79 3.52 4.02 3.85 3.62 3.82 2.32 5.73 2.91 1.8

P2O5 0.28 0.17 0.16 0.17 0.17 0.33 0.16 0.46 0.12 0.54 0.28

LOI 1.78 1.85 1.63 1.03 2 1.02 1.01 1.45 1.7 1.55 1.38

Total 99.11 99.18 98.99 99.47 99.7 99.29 99.16 98.84 99.56 99.97 99.32

Minor elements

U 1.8 3.9 2.3 2.7 3 6.1 2.6 1.5 3.7 2 1.4

Th 7.2 14 12 15 14 18 13 11 16 7.5 6.5

Zr 130 207 130 208 213 287 218 211 185 1364 357

Hf 3.2 5.4 3.3 5.5 5.6 7.5 6.2 17 4.6 27 7.9

Nb 7.5 11 6.1 12 12 18 11 10 13 7.2 5.5

Ta 0.5 0.9 0.6 1 1 1.6 0.9 0.5 1.1 0.5 0.5

Ba 507 728 682 724 729 723 790 1514 647 2470 768

Rb 108 137 121 146 142 143 129 74 250 88 71

Sr 450 286 345 244 228 266 264 597 210 560 639

Cs 15.3 6.5 4.1 5.6 5.7 5.3 5.1 4.3 7.6 2.7 5.1

Ga 20 20 18 19 18 22 19 23 16 29 29

V 206 65 87 66 65 48 55 93 32 65 160

Cr 80 17 34 17 10 10 12 13 10 10 36

Co 22 7.7 10 7.7 10 11 9.7 12 7 15 22

Ni 16 8.2 9.2 4.8 6.1 5.2 5.2 6.3 4.4 6.7 12

Zn 88 55 37 50 64 66 55 64 39 94 99

Pb 8 35 17 26 34 27 29 16 23 23 10

La 25 35 26 33 37 38 36 27 35 30 17

Ce 50 66 47 67 71 79 73 56 65 57 40

Pr 6.6 8.2 5.5 7.7 8.6 9.9 8.8 6.8 7.3 7.7 5.2

Nd 25 28 19 28 32 38 31 26 23 28 19

Sm 5.7 5.3 3.9 5.3 6 8.3 5.8 5.4 4 5.8 4.6

Eu 1.5 1.4 0.8 1.3 1.4 1.9 1.5 2.2 0.8 2.2 1.9

Gd 5.1 4.9 3.3 5.3 5.7 7.8 5.3 4.8 3.8 5.4 4.1

Tb 0.77 0.77 0.47 0.78 0.9 1.26 0.79 0.71 0.57 0.67 0.64

Dy 4.5 4.5 3.1 4.9 5.5 7.4 4.9 4.3 3.5 4.4 4

Ho 0.9 0.91 0.65 1.04 1.12 1.6 0.98 0.91 0.75 0.9 0.83


Peri-

meter

Băiţa

Bihor Pietroasa Budureasa

An

des

ite

Dac

ite

Dac

ite

Dac

ite

Dac

ite

Trac

hy-

dac

ite

Dac

ite

Trac

hy-

and

esit

e

Rh

yolit

e

Trac

hy-

and

esit

e

Bas

asal

tic

and

esit

e

Er 2.3 2.5 1.8 2.9 3 4.1 2.8 2.7 2.1 2.7 2.4

Tm 0.34 0.39 0.28 0.41 0.46 0.64 0.41 0.39 0.3 0.43 0.38

Yb 2.1 2.5 1.7 2.7 3.1 4.3 2.8 2.7 2 2.9 2.6

Lu 0.31 0.37 0.3 0.43 0.47 0.64 0.39 0.43 0.34 0.5 0.4

Y 26 28 20 32 32 45 30 26 24 28 22

Apatite

T (°C) 837 911 901 923 921 962 920 903 919 940 794

Zircon

T (°C) 622 730 690 739 741 752 744 692 752 922 711

Table 3.1 (cont.)

Sample Rb (ppm) Sr (ppm) 87Rb/86Sr 87Sr/86Sr

R06 81 543 0.43 0.705066

R10 80 585 0.4 0.707469

R11 108 450 0.69 0.706317

R21 146 244 1.73 0.708449

R27 74 597 0.36 0.706750

R39 163 169 2.79 0.709487

R44 94 267 1.02 0.707916

R46 71 304 0.68 0.707504

R50 77 240 0.93 0.707672

R54 114 220 1.5 0.708273

R62 94 322 0.84 0.707910

Table 3.2 Whole-rock Rb–Sr isotopic data for the North Apuseni Mts (Auwera et al, 2015)


Mineralising fluids, saline mine waters and shallow ground waters are reasonably well characterised

(e.g. by mineralogical studies, stable isotope, geochemical studies etc).

Fluid circulation is reasonably well understood in the shallow subsurface.

An ore-deposit, at Băița Bihor is in operațion, and there is the possibility of new data aquisition

depending on the requirements of the project.

We could collect samples of mineralisation rocks from the mining galleries (about 300 m below

surface).


Much of the primary data that exists is related to the shallow sub-surface (<1,000 m, and often <200

m). Hence little is known about fluids existing at depths below 1,000 m, both in terms of chemistry

and circulation.

There is no possibility of having samples from deep wells.



3.4.1 Lithology of karst in Bihor Mts

The analysis of the relationship between orebody and hydrogeology of the region defines the study peri-

meter, that includes Bihor Mountains and Beiuș basin. Within the geological constitution of Bihor Mountains,

limestones and dolomites are prevailing, followed by sandstones, conglomerates and igneous rocks.

Considering its extent, the variety and amplitude of the karstic landforms, the topography of the karstic type,

ranks this specific region in the top position among all Romania’s karstic territories (Orășeanu, 2010).

The Bihor Mountains are characterised by broad surfaces of contact zones between karst and volcanic or

plutonic rocks. Contact metamorphism is specific to these areas, as described in chapter 3.3. The importance

of these contact zones between mineralized magmatic (metal generation units) and carbonatic rocks have to

be emphasized; karst is the main transporting agent of the fluids to Beiuș Basin. There are three structural

units which, together, are called Bihor Mountains, from which Crișu Negru, Someșu Cald and Arieșu Mare

rivers originate.

Vlãdeasa massif consists mainly of intrusive and effusive formations, surrounded by sedimentary rockss.

Among these, carbonate rocks are represented by: the karst area Meziad – Ferice – Valea Rea situated to the

west and south-west, and the graben of Someșul Cald situated to the east and south-east.

The central compartment, Bihor Mountains, is widely developed, and is separated from Vlãdeasa Mountains

by Someșu Cald and Crișu Pietros river courses. To the South, Arieșu Mare and Crișu Bãița streams delimit

this compartment with respect to Biharia massif, made up of crystalline schists.

Bihor Mts display a wide variety of structural and lithological assemblages, but 5 types of deposits can be

distinguished, as having distinct hydrological features. They are represented represented on the hydrological

map and can be described as follows (see Figure 3.11):

1. Mesozoic carbonates series, (a- limestones, b- dolomites, c- undivised) and Paleosoic d- crystalline

limestones and dolomites, highly fractured and karstified, characterized by very high effective

infiltration and prevailing conduit porosity with intensive groundwater flow. They generate

numerous karst systems with various size and dominant binary type. Thet host important water

resources in large karst systems. Spring flows up to 550 l/s.

2. Paleozoic granites (a1), and ryolites (a2) Mesosoic ophyolites (b) Laramian intrusive (c1) and volcanic

magmatites (c2), and neogene volcanites (d) and metamorphites (e), with extensive fracture

networks, and developed wathering zones, which provide a continuous and important supply of

rivers flow and binary karst systems.

3. Prevalent molasse deposits (sandstones, conglomerates and less frequently argillaceous shales) with

double porosity. The groundwater is mostly confined to the fissure and stratigraphic joints and less

to intergranular pores. At large thickness, they act as an impervious barrier for karst water reservois

and frecquently form the bedrock and/or caprock for these. a- Permo–Mezosoic Molasse, b- Upper

Cretaceous cover and Miocene transgrassive deposits.

4. Pannonian deposits: marls, argillaceous shales, sands, gravels - (a), Pleistocene deposits - (b), and

Holocene (c) deposits: sands, gravels, clays, hosting discontinuous water accumulations in more

permeable terms.

5. Upper Cretaceous and Miocene marly and argillaceous deposits, devoid of groundwater flow, and

flysch-like series, including rock-complexes of variable permeability (marls, argillaceous shales,


sandstones, limestones) hosting occasionally discountinous aquifer accumulations. (a-Paleozoic; b-

Upper Triassic – Early Jurassic; c-Titonian – Hauterivian; d-Upper Cretaceous – Miocene.

Figure 3.11 Hydrogeological map of the Bihor Mountains karst areas (Orășeanu et al., 2010), according to the

works of Bleahu et al., 1981, Bordea & Bordea, 1973, and to the sheets Avram Iancu (Dumitrescu et al.,

1977), Poiana Horia (Bleahu et al., 1980), Pietroasa (Bleahu et al., 1985), Rãchițele (Mantea et a., 1987) and

Biharia (Bordea et al., 1988) of the geologic map of Romania, scale 1: 50,000. The legend details are included

into the text of the report

3.4.2 Short hystorical review of the Bihor Mountains karst hydrology investigation

In the 1950-1970 period, the first fluorescein tracing experiments in Bihor Mountains have been performed

by M. Serban et al., 1957, Viehmann, 1966, Rusu et al., 1970, the flow connections between Ocoale closed

catchment area and the springs at Cotețul Dobreștilor, respectively the existence of the underground flows

along the Padiș - Poiana Ponor - Cetãțile Ponorului - Galbenei spring lineament being outlined as a result.

During 1976-1985 L. Valenas - alone or in cooperation, publishes in a series of papers the results of

speleological investigations, which assumed a definite hydrologic character too, conducted in the karst of

Bihor Vlãdeasa Mountains and which have brought important contributions in this domain, as an outcome of

the exploration of Groapa de la Barsa cave system (1977-1978), of Coiba Micã - Coiba Mare cave system

(1978), of the cave in Pârâul Hodobanei (1982), of the karst at Casa de Piatrã (1976), in the upper reaches of

Someșu Cald (1978), Lumea Pierdutã (1982) and in other areas.

The hydrogeologic investigations in Bihor Vlãdeasa Mountains have been initiated in 1983 through the

activities conducted by I. Orãșeanu and Nicolle Orãșeanu. During 1983-1985 they perform the first hydro-

geologic mapping of the karst areas, as well as the groundwater reserves evaluation, and done some 30 new

tracer experiments. The description of karst region afferent to our study perimeter area based on the


research described within the volume Karst Hydrogeology of Romania, having Iancu Orășeanu and Adrian

Iurkiewicz as authors.

3.4.3 Orohydrography of the Bihor Mountains

Orohydrography of the Bihor Mountains is represented by Crișu Negru, Someșu Cald and Arieșu Mare

catchment basins. The most important for our study is Crișu Negru catchment basin, because it is the river

basin which connects Bihor Mountains to the eastern part of Beiuș Basin. The flow regime of both surface

streams and groundwater in the karst area of the upper Crișu Bãița catchment basin were dramatically

influenced by the mining activities.

3.4.4 Karst systems

Karst systems in Bihor Vlãdeasa Mountains are generally of binary type. They display a wide variety of

dimensions, lithologic constitutions and dynamics that are mirrored by the physical, chemical and

hydrogeological characteristics of the springs.

The karst springs are situated at different elevations, as a result of the pronounced dissection of the

carbonate deposits and of the rugged topography. At the scale of the entire karst region a general base level

cannot be outlined, each specific karst area having its own base level. The karst springs flow rates extend

over a very wide range, with a 550 l/s maximum annual average value. So far, in Bihor Vlãdeasa Mountains

there have been conducted 59 tracer tests which resulted in outlining 75 underground flow paths.

The average elevation of the sinking points is 1084 m, while that of the outlets is 812 m, the distance

between a sinking point and an outlet being 2098 m on the average, while tracers flowed at an average

velocity of 65.5 m/hour (computed by considering the first tracer arrival). The longest distance between a

sinking point and an outlet (4600 m) is that which separates the pothole in Hoanca Urzicarului from Pãuleasa

spring, while the maximum elevation drops (665 m) is that recorded between the underground stream

sinking point in Muncelul cave (the cave in Dosul Broscoiului) and Blidaru spring in Sighiștel Valley.

3.4.5 Hydrogeology of karst areas

Based on tracers and hydrological monitoring studies and in correlation with lithology, and geological

structure, each karst area was described and analysed by Iancu Orășeanu et al., (2010).

Within Bihor Mountains several distinct karst areas were generated by specific geological and tectonical

conditions. Each of these karst areas has its own groundwater dynamics regime, and its own karstic systems.

Extracted from the Orășeanu’s study, some main characteristics of these karst systems re, as follows:

Some of the springs collect their water from karst systems which display feeble inertia and which are

concerned by intense karst processes, being hence highly conductive and subject to a poor capacity of

storage. The rainfall input is filtered only to a small extent; heavy rainfall being immediately followed by

significant flood pulses.

The average cumulated debit of karstic sources systematically monitored in X. 1984 – IX. 1985, was about

3 m3/s. The debit of 1 m3/s, representing an average cumulated debit of other springs in this mountain, must

be considered too.

The memory effect of the catchment basin (Mangin, 1981a, 1981b, 1982,1984) reflecting the groundwater

reserves that sustain the runoff, is high (47 – 123 days) for basins extending on igneous rocks and/or


cristalline schists, and low (15 days) in case of basins extending prevaletly on limestones, or Permo –

Werfenian molasse deposits.

High values of memory effect parameter in case of igneous and cristalline rocks are due to the advanced

development of the weathering layer, that acts as a storage reservoir which slowly delivers the rainfall

derived water. An example is represented by Vlădeasa ignimbritic rhyolites, that form an important

reservoir, most of which being drained by the Drăgan river, and the Sebișel stream.

Besides the Bihor Mountains, that host important ore-bodies that can influence the water quality of the

deep aquifer, we must consider Beiuș basin, where three wells for the exploitation of geothermal water are

situated.

3.4.6 Geological and hydrogeological characteristics of Beiuș geothermal reservoir

In 1996, the well 3001 intercepted a geothermal reservoir at Beiuș. The 2576 m deep well shows a complex

layer structure of the Beiuș basin. The reservoir is located in Middle Triassic limestones and dolomites, at

1887-2450 m depths. A high pumping flow rate and a water temperature of 84°C opened the perspective of

extracting its thermal energy.

Transgex Company has the exploitation license for this perimeter. With state subventions, they realized the

2576 m deep geothermal well between 1995 and 1996. The following strata were intercepted:

0-988 m Neogen – closed with a 13 3/8-inch steel casing

988-1887 m Jurassic (carbonate rocks) – closed with an 9 5/8-inch steel casing

1887-2576 m Middle Triassic (fractured limestone and dolomites) –uncased borehole

It shows that the Beiuș geothermal reservoir, situated about 60 km south-east of Oradea, is not a local,

isolated one, but of regional character.

Well 3001 produces up to 55 l/s of hot water at 83°C, which is the well-head temperature (Transgex

S.A., priv. communication).

The second well, 3003, was drilled during 2004 and 2005, down to a depth of 2360 m (Triassic

carbonatic reservoir). The well has a discharge of 65 l/s and a temperature of 73.4°C.

Transgex S.A. drilled a reinjection well down to a depth of 2140 m, having as avtive layers dolomitic

Triassic deposits intercepted in the interval 1285-2133 m. Pumping capacity is 180 m3/hour, and

pressure of 5 bar.

The geothermal water has a low mineralization (462 mg/l TDS), and 22.13 mg/l NCG, mainly CO2 and

0.01 mg/l of H2S (ref. to table 3.3 for well 3001).


Observations, measurements and analyses performed at the main springs of Bihor Mountains result in the

following considerations:

Temperature of the karst springs ranges between 5.4 and 10°C, directly related to the elevation of

the supplying karst system. Some springs discharge higher temperature flows, as a result of deeper

underground circulations along overthrust or fault planes.

The pH of the discharged water is slightly alkaline, ranging between 7.15 and 7.86;

Computed saturation indexes indicate that the water of most karst springs in Bihor Mountains is

undersaturated in respect to both calcite and dolomite.

Warm and cold springs at Valea Neagrã and the spring Poarta lui Ioanel are supersaturated by

calcite, the latter spring having large associated travertine deposits.


Water of springs in the non-carbonated catchment areas of the binary karst systems is strongly

undersaturated with respect to calcite and dolomite, inducing an intense dissolution of carbonate

deposits. Typical in this respect are the waters of springs originating in igneous formations, with

slightly acid pH value, which explains the intense development of the karst within the carbonate

deposits.

Waters of the karst systems are of calcium bicarbonate, calcium-magnesium bicarbonate and

magnesium-calcium bicarbonate type, depending on the chemical composition of the traversed

formations (limestones and/or dolomites), with TDS values ranging between 125–529.7 mg/l.

Laboratory ICPT Campina

S.C.TRANSGEX

Date of sample 6/14/1999

pH/°C 7.1 Nitrate (NO3) <1

Carbon dioxide (CO2) 163 Nitrite (NO2) <0.1

Conductivity (S/cm/°C) 500 Phosphate (PO4) <.1

Silica (SiO2) 48 Sulphate (SO4) 70.4

Sodium (Na) 19 Alumina (Al) 0.1

Potassium (K) 4.4 Iron (Fe) 1.4

Magnesium (Mg) 20.7

Calcium (Ca) 54.1

Chloride (Cl) 6.89

Table 3.3 Chemical composition (mg/l) for well F-3001, Beiuș


There is a hydrologic database for the watersheds afferent to Bihor Mts and Beiuș Depression.

The karst is relatively well described.

The geothermal ystem is continuously monitored.

We can have information regarding the quality of geothermal water.


There is not a groundwater model yet.


In 1985 the geothermal map of Romania, scale 1: 1,000,000, was prepared by the Institute of Geology and

Geophysics. The authors, Veliciu S., Negut A., Vamvu V., synthetised of all the data acquired by that date.

According to this map the geothermic flux ranges, for Romania, between 21 – 105 mW m-2. For the Beiuș

basin the heat flow density ranges between 90 and 100 mW m-2, indicating an area with important

geothermal potential.

The deep geological structure of the Romanian territory has been subjected to numerous studies carried out

by means of various geophysical methods. Visarion et al (1978) published an article aiming to link the

geothermal data to other geophysical evidence, in order to improve the knowledge on the structure and

dynamics of the crust within the Romanian territory. For this purpose, a characteristic profile was selected

along which most geological and geophysical features display their maximum variability. Apuseni Mts are

included in this analysis. Overlaping the "International profile XI" recommended for the explosion seismology


Figure 3.12 Extract from geothermal map of Romania (Institute of Geology and Geophysics, 1985). Only a

fragment of the north – western part of the country was included, showing the situations for Apuseni Mts.

The green lines = heat flow isolines (mW m-2); the red lines = geothermic isolines at 3000 m depth(°C)

investigation by KAPG and CBGA, the geotraverse under study crosses succesivelly from south-east to north-

west the following main tectonic units of the country: North Dobrogea, the Carpathian foredeep, the Bend of

the Eastern Carpathians, the Transylvanian Depression, the northern part of the Apuseni Mountains and the

eastern border of the Pannonian area.

In order to evaluate the thermal condition of the crust in the section of the geotraverse one has to start with

surface heat flow data. According to the values reported by Veliciu et al., (1977), the surface heat flow

ranges from 43–52 mW/m2 in the North Dobrogea and the Carpathian fore-deep to 60–88 mW/m2 in the

inner part of the Eastern Carpathians and the Apuseni Mountains. The Transylvanian Depression is

characterized by heat flow values of 55–75 mW/m2 while the eastern border of the Pannonian Basin exhibits

the highest surface heat flow exceeding 90 mW/m2.

In the western part of Romania, the thin granitic layer even if it has relatively rich radioactive content cannot

entirely account for the high surface geothermal activity observed here. The considerably energy inflow from

the upper mantle could have been a driving force in the geological evolution of the region as it is suggested

by stronger subsidence of the Pannonian Basin in comparison with tectonic units from the east.

A zone of deep fractures established by seismic survey as well as an area of persistent shallow earthquakes

of low magnitude has been contoured under the North Apuseni Montains (Constantinescu et al., 1974).


An analysis of the heat flow of the main tectonic units in Romania, realised by Demetrescu and Maria

Andreescu, in 1994 shows that the thermal regime of the lithosphere should be derived according, on the

one hand, to the particular tectonic interactions the various tectonic units have been involved in and, on the

other hand, to the investigated depth interval. A steady-state conduction model of the crustal temperature

field based on the heat flow distribution and information on the structure is presented for the Romanian

territory. The heat flow map is based on available heat flow data (167 heat flow values by the end of 1981),

supplemented, in areas of poor coverage, with estimations from temperature and thermal gradient

information from oil industry boreholes).

Most of the 167 heat flow values were obtained by temperature measurements down to 500–1000 m in

thermally stabilized boreholes and conductivity measurements or estimations for the same depth interval

(Demetrescu et al., 1991b). The heat flow contours are shown by broken lines in areas for which no

(Southern Carpathians) or very poor (e.g. Apuseni Mountains, Western Transylvanian Basin) geothermal

information is available.


The geothermal potential was evaluated based on a relatively low amount of data, but it is

correlated with geophysical measurements.

For the geothermal system in operation there is the possibility of experiments, depending on the

requirements and needes of the project.


There is still significant uncertainty about the temperatures that might exist at the depth of an EGS system as

most estimates and models are based on extrapolation of near surface historical data.

3.7 Current metallogenetic models (2D- and 3D-)

Within Bihor Mts there are three areas (Pietroasa, Budureasa and Băița Bihor) that meet some preconditions

to be counted as possible pilot locations, such as:

the existence of mineralized zones in skarns, resulting from contact metamorphism in the aureoles

of intrusive bodies;

existence, in the Bihor Mountains, of carbonate deposits with regional expansion, which can be

found in Beiuș Basin too, and which host the geothermal aquifer;

intrusive bodies are situated in the proximity of Beiuș Basin, which is an area that has a high

geothermal flow (greater than 90 W/m2), confirmed by extracting significant geothermal resources,

which shows a temperature of 84C at wellhead.

3.7.1 Pietroasa and Budureasa sites

Pietroasa and Budureasa represent large intrusive bodies, mainly granodioritic, associated to the huge

pluton from Bihor Massif, Apuseni Mountains (Stoicovici and Sălăgean, 1970; Borcoş and Andrei, 1988 - in

Borcoş and Vlad, 1994). They belong to the second stage of the Laramian magmatism (Ştefan et al., 1988 and

1992). Several dacite, rhyolite and rhyodacite dykes, striking NW-SE, are crossing the two bodies. The final

magmatic stage generated later several basic dykes (basalts, lamprophyres).

The intrusion of the Late Cretaceous granodioritic magma from Pietroasa (in the south) and Budureasa (in

the north) into the surrounding sediments generated extended and complex contact aureoles. Permian

siliciclastics and Mesozoic dolomites to limestones at the contact zone appear as hornfels, skarns, or more


general, as hydrated metasomatic rocks (Rafalet, 1963; Istrate & Udubașa, 1981; Ionescu, 1987, 1996b,

1999; Ștefan et al., 1988; Marincea, 1993). Within the Anisian dolomitic and calcareous protoliths large

brucite-bearing zones occur in the contact aureoles of the granodioritic intrusions. They form two main

deposits: Pietroasa and Budureasa.

Figure 3.13 Heat flow distribution on the Romanian territory; contours in mW m-2. Dots represent surface

heat flow data points (after Demetrescu et al,1991). EC=East Carpathians; SC=Southern Carpathians; AM-

Apsueni Mts; EEP=East European Platform; MP=Moesian Platform; PD=Pannonian Depression;

TD=Transylvanian Depression; NV=Neogene volcanites; A-A’=possible direction of the cross-section of the

Figure 3.15; O-O’=trench line; rectangle = epicentral area of intermediatedepth earthquakes (Demetrescu

and Maria Andreescu, 1994)

The Pietroasa and Budureasa plutons were emplaced within a time range of 70-74 Ma (Bleahu et al., 1984).

Late dacite and rhyodacite dykes, sometimes up to 15 km in length, crosscut the intrusions. According to

Ionescu and Har (2001), despite the unitary appearance of the Bihor Mountains banatitic magmatism, the

petrochemical studies reveal some differences between the Budureasa and Pietroasa igneous bodies.

Generated in the same structural frame (continental arc granitoids), the Budureasa magmas preceded in

time the more alkaline Pietroasa magmas. The petrochemical differences observed between the Budureasa

and Pietroasa banatitic bodies are at variance with the presence of a single, deep situated, batholith with

large apophyses (as the Budureasa and Pietroasa bodies were considered).

According to Corina Ionescu & Hoeck, (2010), the differences between the Pietroasa and the Budureasa

intrusives are complex. The more SiO2-poor composition would suggest an earlier crystallization of the


former than the latter within the overall evolution trend. This is not consistent with the relative enrichment

of Fe, Mg, Ti and the depletion of Al in the Pietroasa rocks. This requires, compared with the overall trend,

additional processes. Possibly granodioritic to quartz monzodioritic magmas may have assimilated Al-poor

but Fe, Mg and Ti-rich minerals, i.e. amphiboles or clinopyroxenes, which altered the composition in the

appropriate way. This assumption is also supported by the presence of numerous basic xenoliths in the

granitoids from Pietroasa. Similar xenoliths are observed elsewhere in the Apuseni banatites but in a lower

amount, as for example in the Budureasa intrusion.

3.7.1.1 Brucite deposits

Between 1982 and 1990 the brucite deposits from Budureasa and Pietroasa were investigated by surface

pits, drillings and underground galleries. The brucite-bearing zones were sampled at 1 m spacing resulting in

an enormous wealth of analytical, mainly chemical data (Ionescu, 1999).

A schematic and idealized view of the contact of granodiorites with the Anisian dolomites shows a structure

with four zones, ranging from granodiorites to pure dolomites (Ionescu & Hoeck, 2005):

1. Granodiorites are holocrystalline hypidiomorphic, sometimes porphyritic, with large feldspar

phenocrysts. Various magmatic, metamorphic and sedimentary xenoliths are common at the

periphery of the intrusion.

2. Mg skarns, forming the innermost zone of the contact aureole, consist mainly of forsterite, garnet

(andradite) and clinopyroxene (diopside, hedenbergite). Periclase and spinel occur as well. A wealth

of hydrated minerals mainly serpentine minerals, phlogopite, talc, chlorite, epidote–zoisite, apatite,

tremolite–actinolite and subordinately hydrogarnet, vesuvianite, chondrodite, clinohumite,

hydrotalcite, brucite, hydromagnesite and pyrophyllite were also formed. Younger veins with quartz,

magnesite, sepiolite, calcite, pyrite, pyrrhotite, sphalerite, chalcopyrite, galenobismutite, and galena

are common. The skarn thickness around the granodioritic body is relatively small, ranging from 0.5

up to maximum 7 m. The first occurrence of hydrogarnet and magnesioferrite in Romania was

described from the Budureasa area by Ghergari & Ionescu (2000).

3. Brucite-bearing zones occur only at some distances (0.5 to 7 m) from the contact. The irregular,

sometimes lens-shaped brucite-bearing zones range from several metres up to tens of metres in

width and from tens to several hundreds of metres in length, respectively. The thickness of the

brucite-bearing zone can significantly vary within the short distance. The variation of brucite content

across the contact aureola around the granodioritic intrusion is highly inhomogeneous, ranging from

brucite-rich, with up to 40 wt% brucite to brucite-poor domains, with less than 5 wt% brucite. The

average content of brucite is around 10.5 wt% in the Budureasa area and 7.5 wt% in the Pietroasa

area, respectively (Ionescu, 1999).

4. Recrystallized Anisian dolomite, without or with only very low Si and Al content, follows the brucite-

rich zones. Brucite forms small lamellae of 20×20×2 μm up to 80×50×6 μm (length, width, thickness).

Large individual lamellae, over 1 mm in length are only exceptionally found. Brucite lamellae group

in clusters of various shapes and sizes (in average from 0.05 to 1.3 mm). Fillings of small veinlets or

isolated lamellae are rare.

The studies carried out on the mineralogy, petrology and genesis of the brucite deposits reveal a model of

heating and cooling sequence under conditions of very low XCO2 during the contact metamorphism (Ionescu

& Hoeck, 2005). The pressure estimates for the heating and cooling paths can be based on field relations.


The stratigraphic column of sediments covering granodiorites at the time of the intrusion ranges from 2.5 to

4 km (Bleahu et al., 1985), approximately equals to 0.1–0.2 GPa pressure for the contact metamorphism.

The brucite-bearing assemblages were described by Ionescu & Hoeck (2005) in the model system CaO–

MgO–SiO2–H2O–CO2, with calcite–dolomite–periclase–brucite–forsterite–antigorite–(+magnesite–tremolite–

quartz) as main mineral phases. The stability fields for the main dolomite-bearing assemblages in the

Budureasa and Pietroasa brucite deposits show that the stability field of brucite is restricted to the very low

XCO2 (< 0.05) over a wide range of temperatures, up to approximately 610°C.

According to the reaction (1) Brucite = Periclase +H2O the upper stability limit of brucite at 0.1 GPa pressure,

is at 600-610°C. Lower temperatures, below 400°C, can be estimated from the reaction 20 Brucite +

Antigorite = 34 Forsterite + 51 H2O. The reaction Dolomite + H2O = Brucite + Chalcocite + CO2 can take place

over a wide range of temperatures.

Based on field observations and theoretical considerations it is concluded that brucite formed by three main

processes: a) a prograde reaction, which generated periclase in the close vicinity of the intrusion, followed

by a retrograde reaction forming brucite in the presence of a vapour phase; b) directly from dolomite at

lower temperatures and c) by decomposition of forsterite.

3.7.1.2 Borate deposit

In the middle basin of the Aleului Valley (Bihor Mountains), at its confluence with the Sebisel Valley, at the

Gruiului Hill, an important endogene borate deposit, including ludwigite and szaibelyite, pointing to the

kotoite presence, was identified. The mineralized site is situated at about 4 km NE of the locality of Pietroasa

(Bihor District). The occurrence, investigated by mine workings, had also been pointed out (Stoicovici, Stoici,

1969; Stoici, 1974). In 1992 this deposit constitutes the study object of a thorough mineralogical study,

realised by S. Marincea.

The ore deposit is hosted in a zone with magnesian hornfels (sensu Turner, Verhoogen, 1960), at the contact

of the Pietroasa banatitic pluton with Anisian dolomite limetones of the Ferice Nappe (see Bordea, 1973, for

details).

The data analysed by Marincea, (1992) consisting of mineralogical and physico-chemical study of szaibelyite

and associated minerals in the Gruiului Hill occurrence, correlated with general geological aspects led as to

the following conclusions:

The formation of the borates from the contact aureole of the Pietroasa granitoid body is the result

of an infiltration metasomatic process. This process explains the frequency of the occurrence of

ludwigite disseminations in other parts of the contact aureole of the body (Rafalet, 1963). In case of

the Gruiului Hill occurrence the significant boron-fluorine supply implies large metasomatic

processes compatible only with an intense diffusion metasomatism.

The hypothesis of a diffusion metasomatism implies the tectonic control of the boron minerals

disposition in case of the Gruiului Hill occurrence. This hypothesis, also supported by Stoicovici and

Stoici (1969), is based on the location of the mineralized zone nearby a Major fault of the Galbenii

fracture system (with a NW-SE disposition): Tirău-Măgura Guranilor Fault, at its intersection with a

network of conjugated fractures.

The presence of minerals with potential fluorine contents (clinohumite can contain up to 4 per cent

F according to Aleksandrov, 1982) makes plausible the hypothesis of the boron transport as fluoro-

boric compounds with alkaline solutions as an age. (Barsukov, Egorov, 1957). The interaction with


the dolomitic background makes possible the decrease of the alkalinity of such solutions, necessary

for borate precipitation.

Iron seems to be the primary precipitant of boron, as indicated by ludwigite formation before the

pure magnesian borates. The iron deficit in the system would make possible the synchronous

crystallization of such borate (that is of suanite or fluoborite) as well as the later crystallization of

kotoite (Barsukov, Egorov, 1957).

Boron-(fluorine) metasomatic supply is unique, influencing the preservation of the pure magnesian

character of the primary borates, imprinted by the paleosome origin. The character of these borates,

highly susceptible to the acceptance into the network of cations like Mn+, Sn4+, Ti4+, induces the

extreme magnesian character of the Gruiului Hill szaibelyite, for which the secondary genesis has

been admitted.

The constancy of the magnesian contents in calcites occurring in areas with hornfels affected or

unaffected by the boron metasomatism (see point 2) leads to the conclusion of the extension of this

metasomatism in zones where the limited development of the silicate minerals made possible the

formation of an "excess" of magnesium available in the carbonate phases. The reverse correlation

between the abundance of the silicates and the abundance of the boron minerals implies the active

role of the lithologic control in the location of the Gruiului Hill mineralization.

3.7.2 Băița Bihor site

As the majority of Romanian skarn areas, the skarns at Baita Bihor are developed in the contact aureole of an

important body of "banatites" (a major granite- granodiorite intrusion of Late Cretaceous - Paleogene age).

The banatites at Baita Bihor belong to an extended pluton (the Southern Bihor batholith) and were ascribed

by Stefan et al. (1988) to the second cycle of the laramian magmatism in the Apuseni Mountains (Danian-

Ypresian in age). Calcic and magnesian skarns largely develop within the contact aureole. They have as

protolite Mesozoic sedimentary formations belonging to some structural units individualised as the Codru

Nappes System (the Vetre, Urmat and Vălani Units) and the Bihor Autochthon (the Bihor Unit): Bordea,

Bordea (1973).

As a peculiarity, the magnesian skarns at Baita Bihor materialise metasomatic columns described as bodies

by Stoici (1974) or by Cioftica et al. (1977). They are preferentially hosted by some areas of dolomitic

marbles or magnesian hornfels resulting from the thermal metamorphism of the dolostones in the Vetre

Unit (the Frăsinel dolosparite, of Carnian – Norian age) and in the Vălani Unit (the Obârșia Izbuc Formation,

of Anisian - Carnian age). Magnesian skarn bodies were described by Stoici (1974) at. Baia Rosie, Bolfu -

Tony, Hoanca Motului, Antoniu, Sturzu and Martha.

From the mineralogical point of view, the magnesian skarn assemblages consist of forsterite, spinel,

clinohumite, humite, chondrodite, diopside, phlogopite, tremolite, dolomite, calcite, with superposed talc,

serpentines, and brucite. They show strong disequilibria with scarce or no paragenetical intergrown phases.

Mineralizations of iron oxides, magnesian borates, base-metal sulphides and Bi-sulphosalts were recognised

to overlap on the magnesian skarn areas (Cioftica, Vlad, 1968; Stoici, 1974; Cioflica et al. 1977).

According to Stoici, (1983), at Băița Bihor there are the following are types of deposits: metasomatic bodies,

columns, veins, impregnations, lenticular sheet lenses and layers.

Metasomatic bodies are localized along fractures with a regional alignment that coincide with the contact

between a carbonated rock and intrusive body. A classic example is the contact Blidar, along which there

have mineralized skarns, with a thickness of 5 to tens of meters, which are opened by mining works over a

length of 600 m and a height difference of 500m.


Columns are widespread in the Baita Bihor. They are situated at the intersection of two fault systems (Baia

Roșie, Sturzu, Antoniu) at the incidence place of a dyke with a fault system (Bolfu - Tony, Hoanca Moţului), or

in tectonic zones between two eruptive veins (Gustav, Reichenstein). Veins are less widespread, and

impregnations are widespread, but with an insignificant economic importance.

Polymetallic sulphide and Iron mineralization from Băii Valley have form of lenticular layers, consistent with

blastodetritic complex schits. The lenses are the result of residual aluminum and iron accumulations (Sighisel

Valley, Valea Seaca).

The contact-metamorphic zone at Băița Bihor is developed over a wide area (many square kilometers) owing

to the influence of an unexposed intrusive body, the Bihor batholith. The batholith consists mainly of

granodiorite and granite porphyry with subordinate quartz monzodiorite and diorite (Stoici 1983, Ștefan et

al. 1988). A whole-rock Rb–Sr isochron age of 70±5 Ma has been reported for granodioritic rocks of the Bihor

batholiths (Pavelescu et al. 1985). This is some 10 Ma younger than a K–Ar age of 81 Ma reported for similar

rocks in satellite bodies by Bordea et al. (1988), but older than other K–Ar ages (in the range 50–61 Ma)

mentioned by the same authors (Bordea et al. 1988). The intrusion may be consequently assigned to the

most important magmatic event in the region, the “banatitic” one, of Upper Cretaceous – Paleocene age.

The influence of calcium and magnesium metasomatosis, and these lithologic-petrographic and tectonic

factors, led to the formation of important masses of skarns. Depending on the rock that generated the suite

of neoformation minerals, skarns are of several types: calcic, magnesian, calcic – magnesian and

microdiopsidic.

Figure 3.14 Sketch representing Baita Bihor Cu (Mo, Zn-Pb) skarn location (Ciobanu et al. 2002). Deeper parts

of Antoniu have grades of 1-2 g/t Au in bornite ore, also rich in Ag, and Bi. 2 Mt of Gold are target for the

present exploitation.


Calcic skarns, having wollastonite, garnets (grossular and andradite), vesuviane and calcite, and as secondary

minerals: diopsid, hedenbergite, zeolits, fluorine, quartz, apatite, bustamite, are connected to industrial ore

of Mo, Bi, W, with important content of Cu, Pb, Zn, Au, Ag.

Calcic – magnesian skarns are formed mainly by dipside and calcite, which contain a suite of minerals, from

oxides and sulphides class, which were exploited since the last century.

Microdiopsidic skarns are characteristic for the veins situated within Băița Molybden ore-body.

Magnesian skarns are described below (see Marincea, 2001):

Extensive boron metasomatism affected the rocks in the contact-metamorphic zone and is locally

manifested in magnesian skarns developed at the expense of sequences of dolostone of Anisian – Carnian or

Carnian – Norian age (Bordea et al. 1988). Such skarns are commonly boron-bearing and occur in well-

expressed metasomatic columns or “skarn bodies” (i.e., those at Baia Roșie, Antoniu, Hoanca Moțului and

Bolfu–Tony). The skarn bodies, now mostly removed by intensive mining for base-metal sulfides, extended

downward to more than 400 m below the surface; only small exposures may now be observed at the

surface. A geological sketch of the Băița Bihor area is given in Figure 3.14. Stoici (1974, 1983) gave additional

details concerning the geology and mining operations in the area, as well as extensive cartographic

descriptions.

Magnesian borates (i.e., kotoite, suanite, ludwigite, fluoborite, szaibelyite) are found in the outer zones of

the metasomatic columns, whose inner zones generally consist of diopside-bearing skarns. The boron-

bearing skarn is always located at the very contact of the dolomite marble. The abundance of kotoite is

remarkable; for this reason, Watanabe (1939) gave the name “kotoite marble” to this rock. In fact, the

internal zoning of the boron-bearing skarn is more complex, including an external zone with suanite and an

internal one with kotoite (Marincea 1998). Szaibelyite is widely distributed and occurs in all the boron-

bearing skarns. Its modal abundance (up to 30% of the rock volume) is highest in the outer zones of the

boron-bearing skarn bodies, where the mineral extensively replaces suanite (Marincea, 2001).

Figure 3.15 Cross-section representing Baita Bihor Cu (Mo, Zn-Pb) skarn location (Ciobanu et al. 2002). The

intersection of the Antoniu and Blidar faults is considered the main control for this trend (mine geologist O.

Kiss)


Ciobanu et al. (2002) described the link between bismuth tellurides and gold within deposits in the Banatitic

Magmatic and Metallogenetic Belt, describing the situation from Băița Bihor. We extract some data from this

article.

In 2015 a short presentation of the Băița Bihor mine is posted on the internet by VAST Resources PCL, which

has the exploitation license. It states the following:

Mine hosts; copper, silver, zinc, lead, tungsten, gold, molybdenum, bismuth and antimony;

Depth potential below the deepest Level 18 has only been drill tested for about 90 m – it is not yet

certain how deep the skarn mineralisation will persist before being cut off by an underlying granite

intrusion – see below

The branching skarn geometry suggests the mine is currently in the shallow upper levels of the

system and the deep roots could persist for at least several hundred metres – an old Russian hole in

the 1970s indicated +350m from base of mine to granite.

Orebody is zoned vertically with Au-Ag caps and Pb-Zn being richer at upper levels.

Copper grades increase with depth from ~0.8% Cu near surface to >2% Cu below Level 18, with

spectacular Ag and Au grades (200–2,000 g/t and 1–4 g/t respectively) associated with copper on

thin veined contacts with the host dolomite.

Antonio 2 pipe lies approximately 300m north of Antonio 1, both have good access from drives

(galleries) down to Level 18 at Antonio 1 and Level 15 at Antonio 2.

Postulated that the Antonio 1 and 2 pipes may merge at depth forming a substantially larger

orebody representing a priority drilling target.

VAST Resources has rights to mine polymetallic minerals (Cu, Pb, Zn, Ag, Au), molybdenum, bismuth,

wolfram, boron, and wollastonite on exploitation licence LE 999/1999 until 2019, renewable

thereafter in 5 year periods.


A large amount of data (e.g. geochronology, fluid composition, mineralogy, geochemistry, etc.) has

been generated from ore deposit research in Bihor Mountains.

A good understanding is developing of how magmatism, fluids and large-scale structures have

interacted to produce economic mineralisation. This data and knowledge has implications for

engineered geothermal systems.


There is significant uncertainty about the form and scale of mineralisation below 1,000 m.

The distribution of data coverage is generally skewed towards areas where economic mineralisation

has been exploited or commercial mineral exploration has occurred.




More information can be added in order to decipher the relation between the two structural units Bihor Mts

and Beiuș Basin, and to indicate to what extent alpine magmatism that is described within Bihor Mts can

influence the sedimentary basin, from where geothermal water is extracted.

4.1.1 Magnetic and gravity contributions to the deciphering of banatitic structures

The extensive petrophysical studies carried out by Andrei et al. (1989) have shown the main contrasts of

both magnetisation intensity and volumetric density which command the way of reflection of the banatitic

structures in the gravity and magnetic images. Moreover, these studies have allowed to identify the

presence and to establish the importance of other sources of gravity and magnetic anomalies with similar

features to those caused by banatitic magmatites.

The banatitic magmatites cause in most cases positive contrasts in magnetisation, with the exception where

host formations are Moesozoic ophiolites or crystalline series including important masses of metabasitic

rocks. Thus, the banatitic magmatites, in the absence of hydrothermal alterations in argillaceous facies, have

usually values- of magnetic susceptibility of over 1000–1500 cgs units.

Only the main mass of the rhyolites from Vlădeasa show magnetic susceptibility values lower than 100-200

cgs units. The magnetic susceptibility of intermediate-basic banatites (diorites, monzodiorites, gabbros, etc.)

is, as an average, almost double in comparison with that of the acid ones (granodiorite, granite,

monzogranate) especially because of the higher content of ferromagnetic accessory minerals (magnetite,

titano-Magnetite, ilmenite).

In most cases the intensity of natural magnetic magnetization is subordinate to the induced magnetization,

especially in the case of acidic banatites. At the magnetization excess caused by the banatitic magmatites,

there are added, with varying importance, those of the thermal metamorphic aureole either izochemical or

allochemical. In this respect, the most outstanding example was pointed out in the upper part of Bihor -

Vladeasa pluton in v. Leuca — v. Băița area where the Permian deposits of the Arieseni unit have acquired a

high magnetization because of the muschetovitization of the hematitic pigment of rocks under the influence

of izochemical thermal metamorphism on an aureole of around 1600 m. The skarns with magnetite show

large values of magnetic susceptibility in direct connection with the amount of this mineral. The

hydrothermal alterations in argillaceous facies diminish down to cancellation of the magnetic properties of

banatites and associated formations depending on the intensity of these processes.

The acid banatitic intrusive rocks show density deficits of 0.10–0.15 g/cm3 in comparison with crystalline

basement formations, ophiolitic basalts, Permian deposits and several levels of the Triassic. Compared to the

Jurassic and Cretaceous formations, their density deficits are small (sometimes very small), while in

comparison with the granitoids of internal and middle Dacides, as well as with Werfenian deposits in Seiss

facies, the acid banatites do not create any density contrast. The intermediate-basic banatitic intrusive-

bodies usually generate density excesses against the host formations with the exception of metabasic terms

of several crystalline series. The quartz diorites and quartz monzodiorites have a density similar to that of the

mainly metaterrigenous crystalline formations. The hornfelsification processes that influenced the host rocks

cause a minor modification of density while the pyrometasomatic metamorphism brings about an important

increase of the density. The hydrothermal alteration in argillaceous facies of the banatitic rocks causes a

density decrease if no significant pyritisation occurs.


This short picture of the petrophysical contrast reveals that the acid banatitic intrusions cause usually normal

magnetic anomalies, combined frequently with gravity minima especially over areas with crystalline

formations. The intermediate basic banatitic intrusions bring about steeper magnetic anomalies that may be

doubled by gravity maxima. The magnetic anomalies always add the effect of the thermal metamorphism

aureole to that of the banatitic intrusion itself. In case of very deep hydrothermal alterations in argillaceous

facies, the banatitic structures may not disturb the geomagnetic field. In such situations like Masca-Baișoara

and Florimunda - Varad, the magnetic anomalies are caused only by the magnetite ± pyrhotite skarn cover of

the respective bodies.

Figure 4.1 Distribution of depth banatitic structures deduced from aeromagnetic and gravity data (Andrei et

al., 1989) - see the legend on the next page


Figure 4.1 continued

By applying the interpretation criteria described above, the map of banatitic structures from Romania as

inferred from aeromagnetic and gravity structures was elaborated by Andrei et al, (1989). Most of the

structures pointed out are of intrusive type, but sometimes (Vladeasa, Mureș Through and Rusca Montana

basin) the perturbing bodies comprise masses of volcanics and/or epiclastic formations.

Figure 4.1 qualitatively presents the depth and culmination contours of plutonic bodies and also of several

main hypabyssal intrusions. The geophysical map was projected on the study case perimeter map. The result


is shown in Figure 4.2. From this map, the extension of hypabyssal plutonic body can be seen, within both

Bihor Mountains, and the Beiuş basin.

Figure 4.2 Geophysical data projected on the study case perimeter map. Legend for geophysical features: 1.

depth contour of the Bihor banatitic plutonic body=O-----O; 2. contour of culmination of banatitic plutons of

smaller size; +- - - + 2a – acid or undifferentiated bodies; 2b-intermediate or basic bodies. > - - >

4.1.2 Geological contributions to the deciphering of banatitic structures

A team from the Geological and Geophysical Institute of Romania coordinated the elaboration of general

profiles accross Romania, that synthetise all geophysical and geological knowledge gathered from reports.

The team was coordonated by Ștefănescu and, for the Bihor Mountains the following data were integrated:

aeromagnetic, gravimetric and seismic data from: Fl. Ionescu, M. Niculin, L. Popescu – Brădet, V.

Teodorescu, E. Spînoche;

geologic data from: M. Ștefăneacu, Șt. Panin, S. Bordea, I. Balintoni and P. Polonic;


For this study we present a fragment of one of these profiles, 1-A (Ștefănescu et al.), which is a cross-section

between Codru Moma Mts – Beiuș Basin – Bihor Mts, (Figure 4.3). The profile crosses from south west to

north east the central part of the study case perimeter. The section indicates a succession of nappes that

overlie the intrusive plutonic body. According to this cross-section, over Bihor Autochtonous, Vălani Nappe is

extended and, in its turn, is covered by Finiș Nappe. Above them Arieșeni Nappe overlies to the south, or

Dieva Nappe overlies to the north. According to this cross-section one can observe that all these nappes are

to be found in both the eastern part of Bihor Mountains and the western part of Beiuș basin.

Figure 4.3 Cross-section between Codru Moma Mts – Beiuș Basin – Bihor Mts extracted from the profile 1-A

(Ștefănescu et al.). See legends on next page


The IGR holds a large amount of information about the geological, geophysical and geochemical

properties of the Romania.

Data coverage for the Bihor Mts is at a scale 1: 50,000 for geology and 1: 200,000 for geophysics.


IGR has modern mineralogical laboratories that can bring an input to the new data analyses

depending on the project requirements.

4.2 Limitations in our current understanding of Bihor Mountains

The majority of the data sets only relate to the shallow sub-surface 0–1,000 m).

Some datasets are incomplete.

Some datasets are based on old data that are hosted on paper.

for Figure 4.3


5 Concluding remarks

This review of the Bihor Mts has shown their potential for the CHPM project, i.e., extracting metals together

with geothermal waters from larger depth. Here, we summarize data supporting this idea.

5.1 Geological data

Within the Bihor Mountains, a granodioritic-granitic batholitic body, which is of hypoabissal origin, extends,

both at the surface and in the underground up to the Galbena fault. At the surface, within the Pietroasa -

Aleului valley area, and further north, up to Budureasa, granodiorites crop out. Associated with this banatitic

intrusion, apophyses and bodies of andesitic or basaltic composition have been documented, especially in

the upper reaches of Crișu Bãița along the valleys Hoanca Moțului, Corlatu and Fleșcuța, as well as in the

Valea Seacã catchment area. The intrusion of the banatites has resulted in contact processes that affected

the sedimentary deposits being traversed. At the contact of the banatites with the limestones, marbles and

various types of calcidic skarns have been formed, while at the contact with the detritic and pelitic rocks are

met, e.g., hornfels and garnet skarns.

Owing to the Bihor pluton, the Bihor Mts are integrated within the Banatitic Magmatic and Metallogenic

Belt, which represents a series of discontinuous magmatic and metallogenic occurrences of Upper

Cretaceous age, and being discordant in respect to Mid-Cretaceous nappe structures. The most important

occurrences are Pietroasa, Budureasa and Băița Bihor, where the magmatic bodies intruded Permian-

Mesozoic sequences and produced contact-metamorphic aureoles. As a consequence brucite and borates

were reported for skarns from Pietroasa and Budureasa, and Cu (Mo, Zn-Pb), Au and Ag were exploited in

Băița Bihor.

5.2 Geophysical and structural data

The maps from Figures 4.1, 4.2, and 3.13 corroborated with magnetometric and gravimetric field

measurements indicate that the Bihor batolith and its apophyses have regional extention. These intrusions

essentially changed the whole previous geological assemblage. A fault system, mainly oriented from north-

west to south east affected the Permo-Mesozoic deposits from above.

The Codru Nappes System is common to both, Bihor Mountains and Beius basin, overlying the Bihor unit.

Moreover, a succession of several overlapping nappes, each containing Middle and Upper Triassic carbonate

deposits are shown in Figure 4.3. It results in that the sequences of Middle and Upper Triassic carbonate

deposits can be intercepted two or even three times at different depths.

These Middle and Upper Triassic deposits are concurrently:

1. magnesium skarn areas, which resulted from thermal metamorphic processes, providing metals;

2. permeable strata, through which metal rich fluids are transported at long distances, from Bihor Mts

to Beiuș Basin;

3. geothermal aquifers where hot water is extracted.

5.3 Hydrogeology

Being an intense karstified region, the Bihor Mountains are characterised by a very high rate of circulation of

fluids, generating aquifers with large discharge, and with short periods of time for recharging (in case of

intensive exploitation).


Both at the surface and at depth, there are extensive contact areas between the magmatic body and the

carbonated deposits, facilitating the mobility of waters and their enrichment and diversification in chemical

components.

The Beius well 3001 intercepted a productive geothermal layer, represented by the Anisian – Ladinian of

Ferice Nappe, at 2700m depth. According to the section in Figure 4.3, another geothermally productive

sequence of Middle – Upper Triassic deposits may be intercepted at even larger depths.

5.4 Metallogenesis

In our study we include three sites, Pietroasa, Budureasa, and Băița Bihor. They have similarities but also

differences. It is still unclear, which of these sites delivers metals to the aquifer.

At both Pietroasa - Budureasa and Baita Bihor metamorphosed dolomitic layers (dolomitic marbles) are

present, framed by calcic marbles, and similar to those that mainly host karst geothermal aquifers from

Beius.

Such sequences are represented by anisian dolomites from Pietroasa and Budureasa, belonging to the Ferice

Nappe, which contain mineralisations of boron, brucite and, at Budureasa, skarns with magnetite. The

sequences are also represented by Carnian – Norian ‘Băița dolomites and marbles’. They belong to the Vetre

Unit or to the Vălani Unit and host magnesian skarns with boron Molybden and a suite of minerals, mainly

oxides and sulphides.

Metallogenesis conditions determine and even facilitate the mobility of elements in hydrothermal fluids. This

process needs to be deciphered for the skarn deposits from Pietroasa, Budureasa and Băița Bihor, as well as

for boron and magnesian minerals dissolved in aqueous solutions.

5.5 Geothermal data

Visarion (1978), and later Demetrescu (1994) demonstrated that regional geothermal conditions are strongly

influenced by the tectonic and magmatic activity around.

In the Beiuș basin, situated in the proximity of the Pannonian basin where maximum values of heat flow for

Romania of > 100 mW m-2 are observed, heat flow density is estimated value to > 90 mW m-2. According to

Visarion, the thin granitic layer in the western part of Romania cannot entirely account for the high surface

geothermal activity observed here, even though it is rich radioactive elements. A considerable inflow of heat

from the upper mantle could have been one of the driving forces in the geological evolution of the region.

This is also suggested by stronger subsidence of the Pannonian Basin in comparison with tectonic units from

the east. Demetrescu has estimated temperature at 20 km depth beneath the Beiuș basin to c. 500°C.


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CHPM2030 DELIVERABLE D 1.2 APPENDIX 1.2.4

REPORT ON DATA AVAILABILITY: SWEDEN

Summary:

This report aims to provide a brief overview of three major ore districts in Sweden,

including description of the geological setting, and on-going efforts in geophysics in

seeing deeper and increasing resolution for detecting mineralised zones at depth, as

well as attempting to estimate their low to mid enthalpy geothermal potential.

Authors:

Magnus Ripa, geologist, Gerhard Schwarz, geophysicist, Bo Thunholm, hydrogeologist

(Geological Survey of Sweden)

CHPM2030 DELIVERABLE 1.2. APPENDIX 1.2.4

(A1.2.4) 2 / 49

Table of contents

1 Executive summary .................................................................................................................................... 5

2 Introduction and outline of work ............................................................................................................... 7

2.1 Country specific issues ....................................................................................................................... 7

2.2 Goals .................................................................................................................................................. 7

3 Previous research and available data ....................................................................................................... 10

3.1 Structural settings inferred from geology and geophysics (incl. drilling) ......................................... 10

3.2 Geometry and composition of ore deposits .................................................................................... 14

3.3 Structural evolution, deep-seated faults and fracture zones, their alignment ................................ 17

3.4 Hydraulic properties, deep fluid flow ............................................................................................... 18

3.5 Fluid composition, brines, meteoric waters ..................................................................................... 23

3.6 Thermal properties and heat flow ................................................................................................... 25

3.7 Current metallogenic models (2D- and 3D-) .................................................................................... 29

4 Identifying target sites for future CHPM .................................................................................................. 30

4.1 Extending existing models to greater depth, integrating data down to 7 km .................................. 30

4.2 Knowledge gaps and limitations ...................................................................................................... 31

5 Concluding remarks ................................................................................................................................. 32

6 Acknowledgements .................................................................................................................................. 32

7 References ............................................................................................................................................... 32

8 Appendix .................................................................................................................................................. 42


(A1.2.4) 3 / 49

List of figures

Figure 1. a) Bedrock geology of Sweden (SGU data). Insert shows the geographical and tectonic setting of

Fennoscandia. b) (next page) The map of (a), where major ore districts, potential sites for nuclear waste

disposal (SKB test site) and sites of deep drill holes (COSC, Siljan, DGE-1) are noted. Presently active mines

are marked by + ................................................................................................................................................. 8

Figure 2. Geological map of the Skellefte district (SD), where, e.g., reflection seismic investigations of the

upper crust were done (Dehgannejad et al. 2012a) within the GEORANGE3D and the VINNOVA4D projects 12

Figure 3. 3D views and geological models around the Kristineberg mine in the Skellefte district down to larger

depth (Malehmir et al. 2009b). A combination of seismic reflection data (a) and geological cross sections (b),

and final models (c, d) where all geological and geophysical information available was combined for targeting

new prospecting areas ..................................................................................................................................... 13

Figure 4. The location of mines, known deposits and prospects in Sweden as named in text and in table 1

(according to SGU databases) .......................................................................................................................... 15

Figure 5. Boreholes in Sweden mostly drilled for prospection purposes which can provide relevant data for

the CHPM studies (locations from the SGU drilling database) ......................................................................... 19

Figure 6. The Gravberg hole in the Siljan ring of central Sweden (cf. with fig. 1b). a) Lithology with two types

of granites; b) Measured temperature at depth; c) Residual temperature, the difference between measured

– and constant gradient temperature (data measured in 1997 and 2004, with an artificial offset of 0.5°C

introduced); d, e) temperature gradients as running mean values of depth intervals of 20 and 500 m.

Gradient data of section d) are implying the presence of fractures in the bedrock (Balling 2013) ................. 21

Figure 7. Orientation of the maximum horizontal compressive stress in Scandinavia (Heidbach et al. 2008) . 22

Figure 8. Approximately NW-SE/W-E cross-section through the Laxemar-Simpevarp area (SKB 2009). Shown

are: a) the location of boreholes and sections which have undergone hydro-geochemical sampling, b) the

main fracture groundwater types (colour coded) which characterise the site, and c) the chloride distribution

with depth along the major deformation zones. Dotted lines in different colours represent the approximate

depths of penetration of the various fracture groundwater types along hydraulically active deformation

zones ................................................................................................................................................................ 24

Figure 9. Temperature of the uppermost crust in Sweden, at 500 m and 1000 m depth (Hurter and Haenel

2002) ................................................................................................................................................................ 26

Figure 10. Heat production calculated from airborne radiometric data from outcrops all over Sweden (except

of the mountain areas), in µW/ m3 (Schwarz et al. 2010) ................................................................................ 27

Figure 11. Map with corrected surface heat flow in Fennoscandia (Balling 2013), based on measurements at

more than 250 sites (marked by dot)............................................................................................................... 28

Figure 12. The location of seismic reflectors owing to a massive sulphite deposit at about 1200 m depth, and

its position in the 2D- and 3D interpretation (Malehmir et al. 2010): A warning example, demonstrating the

need for proper data coverage and processing to avoid misinterpretations ................................................... 31


(A1.2.4) 4 / 49

Figure A.1. Map of the anomalous total magnetic field over Sweden derived from airborne magnetic measurements (SGU 2016). Typical distance between flight lines is 200 m, measuring altitude either, 30 or 60 m, with data points along flight pass every 17 m.

Figure A.2. Coverage of Sweden by airborne very low frequency (VLF) measurements (SGU 2016). Areas in colour where electrical resistivity of the uppermost surface could be obtained while data of areas in grey represent older data not being methodologically applicable for deriving resistivity.

Figure A.3. Map of Sweden with areas where airborne measurements of natural gamma radiation were done (SGU 2016). Shown here is the concentration of uranium (238 U in ppm) in the uppermost soil and bedrock of the Earth. The other two isotope elements observed are potassium and thorium making it possible, e.g., to identify bedrock units close to the surface and calculate their heat production rate.

Figure A.4. Gravity anomaly map (Bouguer anomaly in mGal) of Sweden (SGU 2016) based on the SGU database with contributions from third parties. Measuring sites account to about 183000, with gridding of data done for areas of 500 x 500 m2.

List of tables

Table 1. Listing of prospects, deposits and mines mentioned in text. Tonnage includes known or estimated

production, reserves and resources. Grades are approximate. N.d.: No data available .................................. 16

Table 2. Boreholes in Sweden with relevant data. X indicates availability of data. X* indicates available data of

various quality and quantity within this group of boreholes ........................................................................... 20

Table A.1. Summary of databases held by SGU and relevant for the CHPM2030 project.

Table A.2. Summary of data in web map services (WMS) – as from the Map Viewer, held by SGU and relevant for CHPM2030. In accordance with INSPIRE access is free of charge.


(A1.2.4) 5 / 49

1 Executive summary

There are four major ore districts in Sweden. These are Bergslagen, the Skellefte field, Northern Norrbotten

and the Caledonides. The latter one is not assessed in this report. A number of mineralisations are hosted by

rocks of the Palaeoproterozoic Karelian Greenstone group, but the tectonic setting of the majority of

occurrences in the Precambrian is a Svecokarelian (c. 1.9 - 1.8 Ga) magmatic arc; most of these are early-

tectonic, but late- to post-tectonic mineralisations occur as well. A number of mineralisations were formed in

relation to the Sveconorwegian (c. 1.0 Ga) and Caledonian (c. 0.4 Ga) continent-continent collisions,

respectively. In addition, greisens-style vein mineralisations in some felsic plutonic rocks (at both c. 1.7 and

1.45 Ga) of anorogenic or unclear relation to tectonic processes and Fe mineralisations in Jurassic

sandstones occur.

Since their formation large volumes of the bedrock in Sweden have been subjected to intense tectonic

deformation and subsequent erosion, and rocks, including mineralisations, and structures originally formed

at some depth in the crust are locally accessible for study at or close to the present surface. Examples of

such mineralisations are structurally controlled iron oxide-copper-gold (IOCG), skarn, porphyry and, possibly,

some rare earth element (REE). In contrast, several mineralisations in Sweden that presently are being mined

at and evaluated to some depths were originally formed at or close to the Earth’s surface, and genetical data

from these may have limited relevance to the present task.

For most of the bedrock in Sweden, the last metamorphic event with regional ductile deformation occurred

at c. 1.8 Ga. Between 1.8 and 1.7 Ga the temperature of the bedrock presently exposed was such low that

brittle deformation has taken place. Locally, rocks were affected by ductile deformation in relation to later

events such as the Blekinge-Bornholm (Danopolonian; 1.5–1.4 Ga), Sveconorwegian and Caledonian

orogenies. Outside these orogens and local shear zones, the bedrock of Sweden has mainly reacted as far-

field brittle response to tectonic events since c. 1.7 Ga.

The Geological Survey of Sweden has a long standing tradition in geological mapping of the country,

especially with the support from airborne geophysics which is motivated by the low degree of bedrock

exposures. Early geophysical investigations at crustal scales or even deeper were mainly done by other

research groups for understanding deep geology and the tectonic evolution of Fennoscandia and its

surroundings. The European Geotraverse (Fennolora), the BABEL project, test profiles in the Skellefte field

and in Norrbotten are all examples of such research projects.

Electrical conductivity studies at crustal and upper mantle scales reported a highly conductive belt in the

Skellefte district, extending laterally more than 150 km and having total conductance of more than 1000

Siemens. This is interpreted as shallow graphitic shales embedded in otherwise resistive crust.

During the last decade reflection seismic investigations were introduced in some pilot studies of larger

extent in Sweden for prospecting after minerals and ores in the Earth’s uppermost crust. The seismic survey,

competing with other geophysical exploration methods was judged as economically more justified. The

Kristineberg area in the western Skellefte district was chosen as well suited for these studies. The chosen

area was in addition well documented by earlier investigations, including boreholes drilled to greater depths

than 1000 m. High resolution reflection seismic data provided detailed images of an ore body of

volcanogenic massive sulphides and associated structures. It´s habit had not been as detailed, and visible in


(A1.2.4) 6 / 49

previous studies. The seismic experiments have also shown that considerable efforts need to be undertaken

in geologically complex areas to properly acquire data, i.e., preferably as 3D- instead of 2D surveys.

Boreholes of several kilometres in depth are fairly rare in Sweden. The deepest boreholes reaching a depth

of 6779 m and of 6529 m are located in the Siljan ring structure in central Sweden. One of these two holes is

still accessible down to about 5500 m. The third deepest borehole was drilled in southernmost Sweden,

close to the city of Lund and reached a depth of 3702 m. This borehole penetrates a thick sedimentary

succession of Mesozoic strata before entering the crystalline basement at 1946 m depth. A large number of

deep boreholes are performed by the Swedish Nuclear Fuel and Waste Management Company (SKB) in their

study and research fields. The deepest hole of 1700 m depth is located in south-eastern Sweden. Recently, a

deep borehole reaching a depth of 2496 m has been drilled in the Scandes within the project Collisional

Orogeny in the Scandinavian Caledonides (COSC). A very large number of boreholes, some of these still

accessible, are located in the ore bearing districts of Sweden, mainly in Bergslagen, Skellefte and Northern

Norrbotten. Few of these holes are reaching depths greater > 1000 m. Over 8000 holes were drilled to > 100

m in depth. SGU is hosting an archive where about 33000 of these boreholes are documented and more

than 3000 km of drill cores are stored (see even tables A.1, A.2 in the appendix).

Our understanding of deep seated fluids in the crystalline bedrock is still rudimentary. In recent years,

extensive studies of hydraulic properties of the basement in Sweden have mainly been done by SKB. The

hydraulic conductivity decreases with depth with a high degree of variability. Investigations in boreholes

indicate that hydraulic conductivity below 650 m depth varies between 10-7 and 10-12 m/s. Data on the

composition of fluids indicate that brines (> 5 % TDS/l) occur far inland at several 1000 meters depth. Their

residence time was estimated to the order of some hundreds of millions years by the analysis of He-isotopes.

In coastal areas down to about 1000 m depth meteoric waters (about 1.5 Ma in age) account for about 80 %

of the total fluid content. Below that depth brines represent 60 – 80 % of the fluid volume. The corrected

geothermal heat flow ranges between 30 and 70 mW/m2 with the lowest values in the northern part of

Sweden. Data on heat production show obvious differences between rock types related to their content in

radioactive elements.

The generally low geothermal gradient of less than 20 oC/km in the crystalline basement of the Fenno-

scandian Shield in Sweden should allow for low- to mid-enthalpy geothermal systems as part of a possible

CHPM unit.


(A1.2.4) 7 / 49



Available data on the bedrock geology of Sweden (fig. 1) derive mainly from observations at the Earth’s

surface. The overall low degree of bedrock exposure (on average < 10 % due to Quaternary till and sediment

cover) in the country means that most bedrock maps are based on results from geophysical investigations.

At best, the maps should therefore be considered as probable two-dimensional (2D) models of possible rock

configuration and structures. Locally, e.g., in some coastal areas, higher degrees of exposure of the bedrock

allow for more accurate models.

From certain sites in Sweden, underground bedrock data are also available. Examples are mines, areas with

infrastructure projects (mainly cities), deep drilling projects and site-investigations for nuclear waste material

(fig. 1).

Large volumes of the bedrock in Sweden have been subject to intense tectonic deformation and subsequent

erosion, and rocks, including mineralisations, and structures originally formed at considerable depths in the

crust are locally accessible for study at or close to the present surface. Examples of such mineralisations are

structurally controlled iron oxide-copper-gold (IOCG), skarn, porphyry and, possibly, some rare earth

element (REE). In contrast, several mineralisations in Sweden that presently are being mined at and

evaluated to some depths (e.g., Garpenberg and Zinkgruvan) were however originally formed at or close to

the Earth’s surface, and genetical data from these have limited relevance to the present task.

2.2 Goals

This report aims on providing an inventory of three major ore districts in Sweden, namely, Bergslagen in

central Sweden, and further north the Skellefte district, and Northern Norrbotten. Where possible, based on

geophysical data and borehole records, the work includes subsurface information aiming on the occurrence,

composition and location of potential deep ore bodies in the Fennoscandian Shield area. We also shed some

light on spatial variations in crustal heat production, heat flow and temperature and discuss to which extent

these parameters may be affected by convection related to groundwater flow. The big challenge is to predict

fracture geometry and permeability at depth in the crystalline bedrock by combining geological and physical

techniques. Though sub-surface information in mining areas in Sweden has increased during the last years,

the work will be more conceptual as large data gaps still exist and much of the information is based on few

data points of regional character.


(A1.2.4) 8 / 49

Figure 1. a) Bedrock geology of Sweden (SGU data). Insert shows the geographical and tectonic setting of Fennoscandia


(A1.2.4) 9 / 49

Figure 1. b) The map of (a), where major ore districts, potential sites for nuclear waste disposal (SKB test site) and sites of deep drill holes (COSC, Siljan, DGE-1) are noted. Presently active mines are marked by +


(A1.2.4) 10 / 49


3.1 Structural settings inferred from geology and geophysics (incl. drilling)

General overviews of the tectonic setting, geology and mineralisations of the major ore districts in Sweden

(fig. 1) are presented in Bergman et al. (2001) and Martinsson et al. (2016) for Northern Norrbotten, Kathol

and Weihed (2005) for the Skellefte district, Stephens et al. (2009) for Bergslagen, and Grenne et al. (1999)

and Corfu et al. (2014) for the Caledonides. A review on geodynamics and ore formation in the

Fennoscandian shield is presented in Weihed et al. (2005). A comprehensive description of the of

Fennoscandian deposits is given in an edited work by Eilu (2012). The most recent overviews on Swedish

metallogeny are the excursion guide books to the SGA meeting in 2013 (12th Biennial SGA meeting, excursion

guide books SWE1-7). The SGA excursion guide books include an up to date general description of the

geological and tectonic evolution of Sweden. Regarding Northern Norrbotten deposits there is also the paper

by Martinsson et al. (2016). The above mentioned works all contain references to specific deposits and their

type.

The Geological Survey of Sweden has a long standing tradition in geological mapping of the country,

especially with the support from airborne geophysics, which is necessary due to the low degree of bedrock

exposures. Since the early 1960’s airborne surveys were performed covering almost entire Sweden, except

for the range of the Scandes. These surveys have acquired data on the Earth magnetic field, gamma radiation

and the VLF electromagnetic field. In addition to these surveys the gravity field of the Earth was measured

using ground based techniques (see appendix, figs. A.1, A.2, A.3, and A.4).

In Norrbotten, a number of base metal (e.g., the Viscaria Cu deposit), skarn iron and banded iron formations

are hosted by the Karelian Greenstone group, but the tectonic setting of the vast majority of mineralisations

in the Precambrian of Sweden is a Svecokarelian (c. 1.9-1.8 Ga) magmatic arc; most are early-tectonic but

late- to post-tectonic mineralisations occur as well. A number of mineralisations were formed in relation to

the Sveconorwegian (c. 1.0 Ga) and Caledonian (c. 0.4 Ga) continent-continent collisions, respectively. In

addition, greisens-style vein mineralisations in some felsic plutonic rocks (at both c. 1.7 and 1.45 Ga) of

anorogenic or unclear relation to tectonic processes and Jurassic sandstone-hosted Fe mineralisations occur.

Early geophysical investigations at crustal scales or even deeper were mainly done for understanding deep

geology and the tectonic evolution of Fennoscandia and its surroundings. To name here some of these

projects, including seismic refraction experiments, like, e.g., the European Geotraverse (Fennolora)

(Guggisberg et al. 1991; Lund and Heikkinen 1987), the BABEL project (BABEL working group 1990), a test

profile in the Skellefte field of 100 km in length (Elming and Thunehed 1991), and another one in Norrbotten

close to Luleå, being about 30 km long (cf. Juhlin et al. 2002). But, already in the 1950’s Båth and Tryggvason

(1962) conducted seismic experiments around Kiruna, using the blastings of the mine as seismic source to

study upper crustal structures connected to the ore body. In the following decades only some few seismic

reflection experiments aiming on exploring ores and minerals, were done in Scandinavia.

Electrical conductivity can tell us something about structures, but the method can also indicate processes in

the crust and mantle. This parameter was studied at larger scales by, e.g., Jones et al. (1983) and Rasmussen

et al. (1987). As a result of magnetotelluric investigations within the Fennolora project, Rasmussen et al.

(1987) reported a crustal zone of higher electrical conductivity, extending laterally more than 150 km,

centered on the Skellefte district (SD) and having at least thickness of 15 km. New magnetotelluric data were


(A1.2.4) 11 / 49

acquired on a larger scale in north-west Fennoscandia by Cherevatova et al. (2014, 2015a, b) and Korja et al.

(2008). These studies confirmed the highly conductive belt in the Skellefte district (total conductance > 1000

Siemens) which is interpreted as shallow graphitic shales embedded in the otherwise resistive crust. Along

the Caledonian Thrust Front in the Caledonides highly conductive alum shales have been identified between

the resistive Proterozoic basement and the overlying nappes, marking the ramp of overthrusting.

For a long time applying reflection seismic surveys for prospecting after minerals and ores in the Earth’s

uppermost crust, was looked upon as economically unjustified. Potential and electrical resistivity methods

were seen as being more powerful and cost efficient in exploring for ore deposits. Since the experiments of

Båth and Tryggvason (1952) it took some decades, until reflection seismics was used in Sweden to any larger

extend for proving its feasibility in exploring ore deposits: Tryggvason et al. (2006) and Rodriguez-Tablante et

al. (2007) studied the Kristineberg area in the western Skellefte district while Malehmir et al. (2006)

extended these investigations further to the East. This part of the SD is well documented by boreholes

reaching depths greater than 1000 m, high resolution potential field data, i.e., magnetic and gravity, as well

as by petrophysical data. The investigations in the Kristineberg area were followed up by employing

magnetotellurics (MT) on one of the seismic lines allowing for the joint interpretation of velocity and

electrical resistivity data (Hübert et al. 2009). Malehmir (2007) has summarized the outcome of this pilot

study: A strong N dipping reflection in conjunction with higher electrical conductivity is interpreted as the

structural basement for the rocks of the Skellefte group (for a map see fig. 2). Postorogenic granitoids were

modeled down to various depths between one and five km (fig.3). Among others , e.g., Garcia Juanatey

(2012), Bauer et al. (2014) and Tavakoli et al. (2012a, 2012b, 2016a, 2016b) further studied the subsurface of

the central Skellefte district, in order to delineate the structures related to volcanogenic massive sulphide

deposits and to model lithological contacts down to various depths, of some hundreds to some thousands of

meters.

In Bergslagen, the areas around Dannemora, Grängesberg and Garpenberg mines were targeted for the

reflection seismic experiments with the purpose to screen the sub-surface for potential zones of higher

mineralization (Malehmir et al. 2011, Place et al. 2014, and Ahmadi et al. 2013). Recently, the Geological

Survey of Sweden conducted temperature measurements in prospection boreholes in these mining areas

(unpublished data).

In Northern Norrbotten, around the Kiruna iron ore mine, Båth and Tryggvason (1962), Juhohunti et al.

(2014), and Holmgren (2013) have reported from seismic reflection experiments, having the objective of

imaging bedrock contacts and the geometry of structures at depth. These studies were accomplished by

reprocessing of VLF airborne data (Abtahi et al. 2016) and by magnetotellurics (Bastani et al. 2016a, 2016b).

The resistivity models show low resistivity zones at various depths and locations almost over the entire study

area, which may be related to occurrences of graphite or sulfide mineralizations in the uppermost crust.


(A1.2.4) 12 / 49

Figure 2. Geological map of the Skellefte district (SD), where, e.g., reflection seismic investigations of the upper crust were done (Dehgannejad et al. 2012a) within the GEORANGE3D and the VINNOVA4D projects


(A1.2.4) 13 / 49

Figure 3. 3D views and geological models around the Kristineberg mine in the Skellefte district down to larger depth (Malehmir et al. 2009b). A combination of seismic reflection data (a) and geological cross sections (b), and final models (c, d) where all geological and geophysical information available was combined for

targeting new prospecting areas


(A1.2.4) 14 / 49

The interpretation of structural settings of individual mineralisations or districts is normally based on

combinations of surface data, core-drilling, geophysical data and 3D- and 4D-modelling. For deeper

structures and mineralisations, geophysical data are often the only available means for 3D evaluation unless

drilling has been performed. Examples of 3D- (and 4D-) modelling that relate to Swedish bedrock conditions

are Bauer (2013), Bauer et al. (2009, 2010, 2011, 2012, 2014), Malehmir et al. (2009), Carranza and Sadeghi

(2010), Kampmann (2015), Skyttä et al. (2009, 2012, 2013), Wareing (2011) and Weihed (2014) (see even fig.

3).

Data on deep drilling projects in Sweden were presented by Erlström and Sivhed (2003), Lorenz (2010) and

Gee et al. (2010). Predictions of structures at depth (c. 500 m) were to some extent evaluated by the

Swedish Nuclear Fuel and Waste Management Company (SKB) at the test sites in Forsmark (Stephens et al.

2007) and Äspö (Wahlgren et al. 2008).


The prospects and deposits that are mentioned by name in the following text are shown in figure 4 and listed

in Table 1. Most pre- and early-orogenic Svecokarelian metal deposits in Sweden were originally formed as

volcanogenic or sedimentary, stratabound (Fe oxide and base metal skarn) or stratiform (Fe oxide and base

metal) mineralisations at or close to the palaeosurface (see references in section 2.1). Their present shape,

position and orientation are, however, mainly controlled by subsequent polyphase tectonic deformation. In

general, they have been affected by two phases of folding and ductile shearing and by brittle faulting.

In contrast, the present shape of the Tallberg Cu-Mo-Au porphyry deposit in the Skellefte district is

controlled by its host rocks, the isotropic to weakly deformed early-orogenic Jörn intrusive complex (Weihed

et al. 1987, Weihed 2001). A weakly porphyry-style mineralised and slightly deformed quartz monzodiorite in

the footwall of the Aitik Cu-Au-Ag deposit in Norrbotten has also an early-orogenic Svecokarelian age

(Bergman et al. 2001; Wanhainen 2005).

In both Bergslagen and the Skellefte district, early-orogenic mafic intrusive rocks locally carry subeconomic

Ni-mineralisations (Weihed et al. 2005). The rocks are variably deformed to almost undeformed.

Many late- to post-orogenic Svecokarelian and younger mineralisations are epigenetic formations in and

related to deformation zones. Such mineralisations, e.g., Nautanen c. 1.8 Ga IOCG (Bergman et al. 2001;

Martinsson et al. 2016); Björkdal c. 1.8 Ga orogenic Au (Weihed et al. 2005) and Harnäs c. 1.0 Ga orogenic Au

(Alm et al. 2003), are largely vein-hosted, and the orientation and shape of the veins are controlled by the

orientation of the deformation zone and their tectonic emplacement in time.

Outside obvious deformation zones, late-orogenic orthomagmatic mineralisations and skarn and porphyry

mineralisations as well as post- to anorogenic greisen veins occur. Associated with the c. 1.8 Ga phase of

mafic igneous activity in the Transscandinavian Igneous Belt (e.g., Högdahl et al. 2004), some orthomagmatic

Ni-Cu mineralisations occur (e.g., Bjärnborg et al. 2015). The late-orogenic Yxsjöberg W-Cu-F skarn deposit

was described by Ohlsson (1979a) and Romer and Öhlander (1994) and the late-orogenic porphyry-style,

Mo-bearing Pingstaberg granite was described by Billström et al. (1988).


(A1.2.4) 15 / 49

Figure 4. The location of mines, known deposits and prospects in Sweden as named in text and in table 1 (according to SGU databases)


(A1.2.4) 16 / 49

Name District Type Tonnage Grade(s) Status Deepest level

Reference(s)

Aitik Norrbotten Porphyry + IOCG >1300 Mt Cu 0.25 %, Au 0.14 g/t, Ag 2 g/t

Active mine Open pit, 450 m

12th SGA Excursion Guidebook SWE5

Bastnäs Bergslagen Orogenic? 4.5 kt Ce ? % Closed mine 120 m Geijer 1921

Björkdal Skellefte Orogenic gold 50 Mt Au 1.7 g/t Active mine 350 m? 12th SGA Excursion Guidebook SWE2

Garpenberg Bergslagen Skarn 160 Mt Zn 4.6 %, Pb 2 %, Au 0.3 g/t, Ag 130 g/t

Active mine 1250 m Rodney Allen pers. com. 2014; SGU

Grängesberg Bergslagen Orthomagmatic-hydrothermal

>156 Mt Fe 60 %, P 0.81 % Closed mine 650 m 12th SGA Excursion Guidebook SWE4

Harnäs Orogenic gold 60 kt Au 2 g/t Closed mine n.d. Alm et al. 2003

Kiruna Norrbotten Orthomagmatic-hydrothermal

>2000 Mt Fe 60-68 %, P 0.04-0.32 %

Active mine 1540 m 12th SGA Excursion Guidebook SWE5

Laisvall Caledonides Sediment-hosted 110 Mt Zn 0.3 %, Pb 3.8 %, Ag 11 g/t

Closed mine <200 m SGU; Eilu 2012

Malmberget Norrbotten Orthomagmatic-hydrothermal

930 Mt Fe 51 %, P 0.5 % Active mine 1385 m Eilu 2012

Nautanen Norrbotten IOCG 16 Mt Cu 1.5 %, Au 0.7 g/t, Ag 5.5 g/t, Mo 64 g/t

Closed mine and prospect

180 m www.boliden.com

Norra Kärr Orthomagmatic 58 Mt REE-oxides 0.59 %, ZrO2 1.7 %

Prospect 12th SGA Excursion Guidebook SWE3

Pingstaberg Bergslagen Porphyry n.d. Mo <<0.3 % Prospect Ohlsson 1979b

Stekenjokk-Levi

Caledonides VHMS 26 Mt

Cu 1.35 %, Zn 2.93 %, Pb 0.31 %, Au 0.27 g/t, Ag 48 g/t

Closed mine Circa 500 m

Stephens 1986

Tallberg Skellefte Porphyry 44 Mt Cu 0.27 % Prospect Weihed et al. 1987

Viscaria Norrbotten VMS 64 Mt Cu 1.05 % Closed mine and prospect

Circa 650 m

avalonminerals.com.au/

Yxsjöberg Bergslagen Skarn 5 Mt Cu 0.4 %, WO3 0.4 %, CaF2 <5 %

Closed mine 300 m SGU; Magnusson 1970; Tegengren 1924

Zinkgruvan Cu

Bergslagen Skarn? 9 Mt Cu 3 %, Zn 0.4 %, Ag 30 g/t

Active mine 1125 m SGU

Zinkgruvan Zn

Bergslagen SEDEX 74 Mt Zn 9 %, Pb 3.5 %, Ag 75 g/t

Active mine 1125 m SGU

Table 1. Listing of prospects, deposits and mines mentioned in text. Tonnage includes known or estimated production, reserves and resources. Grades are approximate. N.d.: No data available

Along the so-called REE line in Bergslagen, REE mineralisations associated with sulphide-bearing and skarn-

altered banded iron formations and limestone-/skarn-hosted Fe-oxide ores occur; the most prominent

example is Bastnäs (Andersson 2004; Jonsson and Högdahl 2013). The age of the REE-mineralising event is

http://www.boliden.com/


(A1.2.4) 17 / 49

debatable, but a preliminary interpretation of geophysical data from the ongoing EuRare-project suggests

that it may be late-orogenic Svecokarelian.

Associated with the c. 1.7 Ga phase of felsic igneous activity in the Transscandinavian Igneous Belt (Högdahl

et al. 2004), some greisen-type veins occur, but are of no economic value (e.g., Ahl et al. 1999).

A REE-Zr bearing c. 1.5 Ga alkaline nepheline syenite complex at Norra Kärr in southern Sweden, east of and

close to lake Vättern, (see map, fig. 4) is described in the 12th biennial SGA meeting, excursion guidebook

SWE3.

In Dalsland and Värmland, in southwestern Sweden, some post-tectonic Sveconorwegian (c. 1.0-0.9 Ga)

either mainly Cu- or Pb-bearing quartz veins occur. A description of the mineralised veins is given by

Johansson (1985). In this region, sediment-hosted Cu-mineralisations also occur. They are most likely

epigenetic in relation to their host rocks, which formed between c. 1.3 and 1.1 Ga.

The autochthonous Ediacaran (c. 590-570 Ma) to Lower Cambrian sandstones at the present eastern

erosional front of the Scandinavian Caledonian Mountains host several Pb-Zn deposits, one world class

example is the deposit at Laisvall (Saintilan et al. 2015). The mineralisations are epigenetic and formed

during the Middle Ordovician in response to early far-field Caledonian deformational events (Saintilan et al.

2015). Allochthonous Ediacaran sedimentary rocks in the Caledonian nappes locally contain Ni-bearing

serpentinites, some of which are or recently have been evaluated for exploitation (see

www.nickelmountain.se). The uppermost Caledonian nappes (Köli) are exotic terranes with local minera-

lisation such as the Ordovician Stekenjokk-Levi Zn-Cu(-Pb) volcanogenic massive sulphide deposit (Stephens

1986).

3.3 Structural evolution, deep-seated faults and fracture zones, their alignment

The majority of the bedrock and mineralisations in Sweden were formed at c. 1.9 to 1.8 Ga during the

Svecokarelian orogeny. The last Svecokarelian metamorphic event with regional ductile deformation

occurred at c. 1.8 Ga, and sometime between 1.8 and 1.7 Ga the temperature of the bedrock that presently

is exposed was low enough for brittle deformation to occur (e.g., Stephens 2010). Locally, mainly in the

south-easternmost and south-western parts of the country, rocks have been affected by ductile deformation

in relation to later events such as the Blekinge-Bornholm (Danopolonian; 1.5 - 1.4 Ga) , Sveconorwegian (1.1

- 0.9 Ga) and Caledonian (c. 0.4 Ga) orogenies (see e.g., the 12th SGA meeting excursion guide books for a

general description of the tectonic evolution in Sweden). Thus, outside these orogens and in local shear

zones, the bedrock of Sweden has mainly reacted as far-field brittle responses to tectonic events since c. 1.7

Ga.

Dating of minerals in fractures at the test sites for nuclear waste disposal at Forsmark (e.g., Stephens 2010)

and Äspö (Drake et al. 2007) gives variably reliable ages of between about 1.6 and 0.28 Ga for their

emplacement. These age intervals may be correlated to the intrusion of Rapakivi rocks and the

Danopolonian, the Sveconorwegian, the Caledonian and the Hercynian (or Variscan) orogenies, respectively.

The Phanerozoic evolution in Skåne in southernmost Sweden, in terms of sedimentation, dyke intrusions,

basaltic volcanism and structures was discussed by Sivhed et al. (1999). Effects of the Caledonian, Hercynian

(Variscan) and Alpine orogenies were identified by these authors in this area.

http://www.nickelmountain.se/


(A1.2.4) 18 / 49


Several kilometres deep boreholes are rare in Sweden. Consequently, data from deep parts of the crust are

available only from a few sites (fig. 5). The following boreholes or groups of boreholes have been selected as

relevant for presentation in this study (see even table 2):

The deepest boreholes are located in the county of Dalarna where drillings have been done at

Gravberg and Stenberg down to a total depth of 6779 m and 6529 m, respectively. The objective was

to find mantle derived hydrocarbons (Gold 1992). At present, the Gravberg hole is accessible down

to about 5500 m, while the Stenberg hole to unknown reasons is dropped at c. 2500 m (Balling, priv.

comm.).

The third deepest borehole is located close to the city of Lund in southern Sweden. Two boreholes

were drilled to a total depth of 3701.8 m and 1927 m. The objective was to investigate prerequisites

for heat extraction. Both holes penetrate a thick sedimentary succession on top of the basement.

The shallower borehole reached only the top of the crystalline basement while the deep one

penetrated crystalline rocks from 1946 m to the total depth of 3701,8 m.

A larger number of boreholes are located at the study and research sites of the Swedish Nuclear Fuel

and Waste Management Company (SKB). In addition, a number of boreholes are located at the SKB

research site at Äspö and a few other sites, too. The deepest borehole is located at Laxemar with a

total depth of 1700 m.

A borehole reaching a depth of 2496 m has been drilled in the Collisional Orogeny in the

Scandinavian Caledonides (COSC) project in the Scandes, close to the village of Åre (e.g., Gee et al.

2010, Lorenz et al. 2015). The objective is focused on investigating the structure and composition of

the Scandes, deep fluid flow, temperature at depth and reconstructing palaeoclimate.

A large number of boreholes are located in the ore bearing districts of Sweden. Usually, the depth of

these holes is not exceeding 1000 m, about 100 holes have reached depths larger than 500 m, and

more than 8000 holes were drilled deeper than 100 m in depth. SGU hosts a database on boreholes

drilled in Sweden where about 33000 drillings are documented and ca 3000 km of drill cores are

archived. Only recently, about 200 km of drill cores from the Skellefte field and from Northern

Norrbotten, as well as ca. 33 km of cores from Bergslagen were photographed and scanned by IR

techniques. Prospecting companies, after having finished the investigations in their respective claims

are obliged to report about their activities. Information provided varies considerably between

companies. Boreholes related to on-going mining activities normally are not reported to the SGU

databases (see table A.1 in the appendix).

The deepest bore holes so far drilled in Sweden, Gravberg and Stenberg are located in the Siljan ring, an

impact structure about 377 Ma old (Devonian age). No data on hydraulic properties and flow measurements

of these boreholes have been found in the literature. But, changes in the temperature gradient at depth (fig.

6) give some indications of fractures in the bedrock where increased flow of water and transporting of heat

may occur (Balling 2013).

https://en.wikipedia.org/wiki/Megaannum


(A1.2.4) 19 / 49

Figure 5. Boreholes in Sweden mostly drilled for prospection purposes which can provide relevant data for the CHPM studies (locations from the SGU drilling database)


(A1.2.4) 20 / 49

Name of borehole or site

North, Sweref99TM

Eeast, Sweref99TM

Depth (m)

Single (S) Group (G)

Objective of drilling

Hydraulic properties

Thermal properties Fluids

Gravberg 6778640 499550 6779 S Hydrocarbons X X X

Stenberg 6769480 494240 6529 S Hydrocarbons - - -

Lund 6172560 388230 3702 S Heat extraction X X X

COSC 7031850 410260 2496 S Research X X X

Laxemar (SKB) 6365800 696500 1700 S Research site X X X

Laxemar (SKB) 6365800 696500 <1000 G Research site X X X

Äspö (SKB) 6699000 676800 <1000 G Research site X X X

Stripa (SKB) 6366000 601000 <1000 G Research site X X X

Forsmark (SKB) 6618700 505400 <1000 G Study site X X X

Finnsjön (SKB) 6692400 660000 <1000 G Study site X X X

Kråkemåla (SKB) 6370600 599000 <1000 G Study site X X X

Sternö (SKB 6221900 490200 <1000 G Study site X X X

Fjällveden (SKB) 6535400 612000 <1000 G Study site X X X

Gideå (SKB) 7045600 698700 <1000 G Study site X X X

Kamlunge (SKB) 7342600 855900 <1000 G Study site X X X

Svartboberget (SKB) 6807200 531000 <1000 G Study site X X X

Björkö 6577771 645519 900 S Reserch (SGU) - X -

Blötberget 6664148 503967 730 S Reserch (SGU) - X -

Dannemora 6679258 659056 700 S Reserch (SGU) - X -

Floholm 6729264 523059 852 S Reserch (SGU) - X -

Garpenberg 6691586 570801 923 S Reserch (SGU) - X -

Kokträsk 7249682 678532 961 S Reserch (SGU) - X -

Kristineberg 7219078 664659 1401 S Reserch (SGU) - X -

Långban 6636326 459263 701 S Reserch (SGU) - X -

Långträsk 7200667 750541 1421 S Reserch (SGU) - X -

Stollberg 6675012 515577 951 S Reserch (SGU) - X -

Zinkgruvan 6517785 504815 1349 S Reserch (SGU) - X -

Ore bearing areas Various G Prospecting X* X* X*

Table 2. Boreholes in Sweden with relevant data. X indicates availability of data. X* indicates available data of various quality and quantity within this group of boreholes

The borehole close to the city of Lund in southern Sweden is located in an area with sedimentary bedrock.

The crystalline basement is encountered at 1946 m. Hydraulic conductivity, storage coefficient and water

flow were measured (Rosberg 2006, 2010). Hydraulic conductivity in the sedimentary bedrock at various

sections from 1427 to 1853 m was estimated from drawdown data and recovery data with obvious

differences depending on the methods. Hydraulic conductivity estimated from drawdown data varied


(A1.2.4) 21 / 49

between 1.1·10-6 m/s and 1.2·10-5 m/s whereas estimations from recovery tests provided values between

4.9·10-7 and 7.2·10-6 m/s.

Figure 6. The Gravberg hole in the Siljan ring of central Sweden (cf. with fig. 1b). a) Lithology with two types of granites; b) Measured temperature at depth; c) Residual temperature, the difference between measured

– and constant gradient temperature (data measured in 1997 and 2004, with an artificial offset of 0.5°C introduced); d, e) temperature gradients as running mean values of depth intervals of 20 and 500 m.

Gradient data of section d) are implying the presence of fractures in the bedrock (Balling 2013)

Available data on hydraulic properties from other deep boreholes are mostly related to studies carried out

by SKB. These investigations of SKB were concentrated at the study sites of Forsmark and Laxemar (SKB

2008; 2009) and even done at the Äspö Hard Rock Laboratory (SKB 2006a). In addition, the study sites at

Finnsjön, Kråkemåla, Sternö, Fjällveden, Gideå, Kamlunge and Svartboberget (Ahlbohm 1995; Laurent 1982)

as well as the Stripa research site (Carlsson 1986) provide a lot of data of interest. The investigations at the


(A1.2.4) 22 / 49

SKB sites were generally very extensive, though the depths of boreholes usually do not exceed 1000 m below

surface. The deepest borehole (KLX02), however, at Laxemar was drilled down to a depth of 1700 m.

Hydraulic tests in these holes provide data on transmissivity at different depth intervals (SKB 2001).

Hydraulic conductivity below 650 m depth varies between 10-7 and 10-12 m/s (Réhn et al. 2008).

The underground part of the Äspö Hardrock Laboratory in southern Sweden consists of a main tunnel,

accessible by vehicle from the surface reaching almost 500 m depth below ground level, and additionally, of

some short blind tunnels at various depths. The laboratory has been used by SKB for extensive tests and

research for the development of a repository of nuclear waste. Finally, it was decided to locate the waste

deposit at Forsmark in central Sweden.

Figure 7. Orientation of the maximum horizontal compressive stress in Scandinavia (Heidbach et al. 2008)

Data from the COSC borehole were evaluated, e.g., by Hedin (2015). An overview of the investigations is

provided by Lorenz et al. (2015). The borehole did not penetrate the bottom of the thrust zone. It was drilled

by using the Swedish National Scientific Drilling Infrastructure, Riksriggen, that has a maximum capacity in


(A1.2.4) 23 / 49

drilling length of 2 500 m. The rig and the equipment around is primarily available for scientific work, but can

also be used in commercial projects. Country wide hydraulic properties of the bedrock down to about 200 m

depth below the ground surface can be calculated by using data from the Swedish Well Archives (Pousette

1988). At present, data from more than 600 000 wells are included in archive. Based on these well data the

calculated hydraulic conductivity is found to have a spatial variability with obvious differences between

regions (Berggren 1998). However, extrapolation of hydraulic properties of the upper part of the bedrock

down to several kilometres depth would most likely provide results with unacceptable uncertainty. Close to

the ground surface the average hydraulic conductivity of the crystalline bedrock is estimated to 10-5 m/s and

at 100 m depth the hydraulic conductivity is assessed to be about10-8 m/s.

The occurrence of fractures in the bedrock is related to the stress field (fig. 7). The magnitude and the

orientation of the components in the stress field govern the size and the directions of the fractures. It should

be emphasized that the hydraulic properties of the bedrock depend on a number of properties of the

fractures (spacing, porosity, direction, dispersivity, and aperture).


Many stratabound and stratiform mineralisations in Sweden are spatially and, in many cases, genetically

related to local, semi-regional and region scale hydrothermal alteration zones (e.g., Frietsch 1982; Lagerblad

and Gorbatschev 1985; Trägårdh 1988; Ripa 1994; Frietsch et al. 1997; Kathol and Weihed 2005). In general,

the hydrothermal systems were based on seawater (variably mixed with magmatic fluids) and led to Na-

enrichment at deeper and K-Mg-Si enrichments at shallower levels in surrounding volcanic strata. In the

same processes, base metals, Mn and Fe were leached from the volcanics and deposited as oxides and

sulphides at the palaeo-seafloor, in favourable horizons or at contacts between strata.

Data on fluids, brines and meteoric waters from deep boreholes are fairly uncommon. Most of the

investigations have been made by SKB down to a few 100 m depth. The borehole KLX02 at the Laxemar site

was extensively investigated including analysis of chemical properties of the fluid (SKB, 2001; 2006b). The Cl-

isotope composition of the brine from 1000 m depth indicates a residence time of approximately 1.5 Ma

(Louvat et al. 1999). The fluid composition in the borehole at Gravberg indicates that the brine (> 50 000

mg/l) occurs at 6000 m depth, corresponding to about 5700 m below sea level (Juhlin and Sandstedt 1989;

Juhlin, et al. 1998), with a maximum salinity of 150 000 mg/l at the deepest level. By analyzing He-isotopes,

the brine’s residence time at depth was estimated to some hundreds of millions of years (Juhlin et al. 1981).

Close to the coastal area of Sweden brines occur at about 1300 m below sea level, which is indicated by data

from the borehole KLX02 (SKB 2001). Salinity at the deepest level of this borehole was 75 000 mg/l.

According to this study, no brines were found at any other borehole in the crystalline basement in Sweden.

However, in the sedimentary bedrock brine was found in a number of boreholes.

The chemical composition of the fluid has been extensively analysed in the borehole at KLX02 borehole at

Laxemar. Meteoric water accounts for about 80 percent of the water down to about 1000 m depth. At

deeper levels, below 1000 m, the brine accounts for 60 – 80 % of the total content (Laaksoharju 1995). The

salinity of the formation fluid in the Laxemar area is visualised in a cross section down to 2000 m depth (fig.

8). At deeper levels in the cross section the salinity values are largely supported by the data from the KLX02

borehole.


(A1.2.4) 24 / 49

Figure 8. Approximately NW-SE/W-E cross-section through the Laxemar-Simpevarp area (SKB 2009). Shown are: a) the location of boreholes and sections which have undergone hydro-geochemical sampling, b) the

main fracture groundwater types (colour coded) which characterise the site, and c) the chloride distribution with depth along the major deformation zones. Dotted lines in different colours represent the approximate

depths of penetration of the various fracture groundwater types along hydraulically active deformation zones

Data from the borehole close to Lund with a depth down to 3 701.8 m provide no detailed information about

the chemical composition of the fluid (Rosberg 2006; Marsic and Grundfelt 2013). The total dissolved solids

(TDS) at the deepest part of borehole were higher than 20 % (200 000 mg/l). However, this borehole was

largely located in sedimentary rocks with the crystalline bedrock found below 1946 m depth.

In the crystalline bedrock brines were only proved in the boreholes at Gravberg and Laxemar. The brine in

the borehole close to Lund is hosted in sedimentary bedrock. This indicates that brine occurs inland at very

deep levels of several 1000 meters, while in coastal areas brines occur at levels closer to the Earth’s surface

(Juhlin, et al. 1998). In comparison, in the deepest borehole in Finland having 2500 m in depth, brines were

found close to the bottom of the hole (Kukkonen 2007; Nyyssönen et al. 2014).

Countrywide data on groundwater chemistry derive mainly from private wells (Aastrup et al. 1995). The data

reflect the chemistry of the bedrock down to a depth of about 100 m below ground level. Extrapolating

these relatively shallow data to deeper levels of several kilometres depth needs to be investigated.


(A1.2.4) 25 / 49


Country wide estimations of the temperature at 500 and 1000 m depth have been presented by Hurter and

Haenel (2002). The pattern reflects differences in the temperature gradient and heat production at depth

(fig. 9), but even climatic effects.

Temperature measurements in the deep borehole at Gravberg have given a gradient of 15–18°C/km with a

temperature of 87.5°C at a depth of 5050 m (Balling 2013). Thermal conductivity was estimated to about

3 W/m K corresponding to values of the corrected geothermal heat flow ranging from 66 mW/m2 at ground

level to 46 mW/m2 at 5000 m depth. Radiogenic heat production in the upper 4700 m of the borehole is

estimated to range from 3.3 to 5.2 µW/m3, while below 4700 m heat production was estimated to reach

2.3 µW/m3.

The deep borehole close to Lund yields a much greater temperature gradient than elsewhere in Sweden,

reaching values between 16 and 27°C/km. Maximum temperature was measured to 85.1°C at a depth of 3

666 m (Alm and Bjelm 2006).

Measurements of temperature and thermal properties in boreholes outside the ore districts were made by

SKB at the study sites of Forsmark and Laxemar (Sundberg et al. 2009). The deepest borehole is located at

Laxemar (1 700 m). The depth of the other boreholes at the two sites does not exceed 1 000 m. The

corrected surface heat flow at Forsmark and Laxemar was estimated to be 61 and 56 mW/m2 respectively.

The temperature gradient at both sites was about 15°C/km. Heat production for different granites in the

Laxemar area ranged from 2.07 to 4.45 µW/ m3.

Temperature measuremenst in the COSC borehole show a geothermal gradient close to 20°C/km with the

bottom hole temperature reaching about 55°C (Lorenz et al. 2015). Heat generation varies considerably

downhole. Further measurements of thermal and hydraulic properties are planned.

Measurements of temperature and thermal properties were made in 17 boreholes in the ore districts of Aitik

and Skellefte (Parasnis 1975). The vertical depth of these holes is ranging between 365 and 780 m and

corrected heat flow was estimated to 50 mW/m2 for Aitik and to 49 mW/m2 for the Skellefte area.

In eight boreholes in the iron ore district of Malmberget and Kiruna, with depth ranging from 287 to 1 100 m

below ground level the corrected heat flow was estimated to 51 mW/m2 (Parasnis 1981).

Heat production of outcrops all over Sweden was estimated using airborne as well as ground based

radiometric measurements provided from the databases of the Geological Survey of Sweden (Schwarz et al.

2010). The map derived from airborne data only connected to known outcrops (fig. 10) shows obvious

differences between bedrock types. The extrapolation of data to deeper levels was not yet tested. The

differences in heat production reflect differences in radioactivity of the bedrock.


(A1.2.4) 26 / 49

Figure 9. Temperature of the uppermost crust in Sweden, at 500 m and 1000 m depth (Hurter and Haenel 2002)

Within a research project at the Geological Survey of Sweden sub-surface temperature and geothermal heat

flow in Sweden is re-investigated, in an attempt to up-grade older data (e.g., Eliasson et al. 1991). Heat flow

is estimated from the temperature gradient measured in existing deep prospecting boreholes and thermal


(A1.2.4) 27 / 49

conductivity measured on drill cores of these holes. The data are used to improve the earlier estimations of

the geothermal heat flow in Sweden (Hurtig et al. 1992; Balling 2013), fig. 11.

Figure 10. Heat production calculated from airborne radiometric data from outcrops all over Sweden (except of the mountain areas), in µW/ m3 (Schwarz et al. 2010)


(A1.2.4) 28 / 49

Figure 11. Map with corrected surface heat flow in Fennoscandia (Balling 2013), based on measurements at more than 250 sites (marked by dot)


(A1.2.4) 29 / 49

3.7 Current metallogenic models (2D- and 3D-)

Most metal deposits in Sweden were originally formed as volcanic-hosted, largely synvolcanic or slightly

epigenetic, stratabound or stratiform mineralisations at or close to the palaeosurface (e.g., Bergman et al.

2001; Kathol and Weihed 2005; Stephens et al. 2009). Their present shapes, positions and orientations are

mainly controlled by subsequent tectonic deformation. Apart from dominantly stratigraphically underlying

hydrothermal alteration zones (see section 2.5) their style of formation has little or no bearing on present

day deep-seated processes. Some of these deposits are or have been mined at or evaluated to considerable

depths (> 1000 m). Major examples are the sulphide mineralisations in the mines at Zinkgruvan and

Garpenberg in Bergslagen (cf. with tab. 1).

The depth and style of formation for the apatite-bearing iron ores is a matter of debate (see e.g., Bergman et

al. 2001; Martinsson et al. 2016). The mineralisations are in part hosted by volcanic and in part by

subvolcanic rocks and thus epigenetic. The actual depth of the mineralising process is however unclear. The

responsible fluids were at least in part orthomagmatic (magmatic hydrothermal), which suggests some depth

in the crust. Deposits of this kind may thus represent fossil analogues to deep-seated hydrothermal activity

in present day corresponding settings. The more prominent Swedish examples are Kiruna and Malmberget in

Norrbotten and Grängesberg in Bergslagen.

Some Svecokarelian late- to post-tectonic and younger mineralisations formed through and in relation to

metamorphic processes. Thus, these mineralised systems also represent fossil, variously deep-seated

analogues to what may be occurring in corresponding present day tectonic settings, and thorough and

detailed descriptions of them may have relevance to the present task. The most promising Swedish examples

in this respect are those mentioned in section 2.2.


(A1.2.4) 30 / 49



In recent years, ore prospecting campaigns in Sweden have not only increased by number but even by their

depth of investigation. Efforts are undertaken looking deeper into the sub-surface and enhancing resolution

for detecting mineralised zones, ore bodies and imaging faults, fracture zones and lithological contrasts. This

is not only based on using traditional potential field methods, like gravity and magnetic methods, but also

applying deep electromagnetic-, e.g., magnetotelluric (MT) and reflection seismic methods. Because of an

often suitable contrast in electrical resistivity between the host rock and the mineralised zone, MT and

especially AMT measurements, make it possible to identify such zones, though depth resolution may not be

satisfying. Reflection seismics, instead, can provide high-resolution images of the underground and sufficient

depth of investigation. Several studies where high resolution seismics was used for mineral exploration and

site characterization were published, e.g., Juhlin and Palm (1999), Malehmir et al. (2006, 2007, 2009a, b,

2011), Tryggvason et al. (2006), Schmelzbach et al. (2007). The limiting factor in applying high resolution

reflection seismic waves, and, in a powerful combination, also electromagnetics (AMT) to screen the sub-

surface is the economy of such investigations.

In the addressed mining areas of Sweden, especially in the Skellefte district combined reflection seismic and

electromagnetic investigations were performed, e.g. within two larger projects, namely GEORANGE3D (e.g.,

Malehmir et al. 2009a, b; Hübert et al. 2009) and VINNOVA4D (e.g., Dehgannejad et al. 2012a, b; Bauer et al.

2011). The technical parameters for the acquisition of reflection seismic data were adopted to explore

structures at even greater depths, though not being exploitable with present day techniques. High resolution

reflection seismic profiles provided detailed images of an ore body and structures around (Dehghannejad et

al. 2010), not being visible in that detail in earlier data collected by Tryggvason et al. (2006). The latter work

resolved structures down to a depth of 12 kilometres and was complemented by electrical resistivity studies

(García Juanatey 2012). Malehmir et al. (2010) give an example of 2D and 3D interpretation of reflection

seismic data, where reflections owing to a massive sulfite deposit at about 1200 m depth are interpreted

with a laterally misfit of about 700 m (fig. 12).These examples show that considerable efforts need to be

undertaken in geologically complex areas to properly acquire data, i.e., preferably having 3D- instead of 2D

seismic surveys – though again limited by economical issues. It should be noted that in 2010 the Skellefte

district was suggested being the location for a deep drilling project. The borehole should provide the

possibility to constrain the established models for the ore district (Weihed 2010) by penetrating the upper

crust down to at least 2500 m. This pre-proposal was a part of the then Swedish Deep Drilling Program

(SDDP, Lorentz et al. 2010).


(A1.2.4) 31 / 49

Figure 12. The location of seismic reflectors owing to a massive sulphite deposit at about 1200 m depth, and its position in the 2D- and 3D interpretation (Malehmir et al. 2010): A warning example, demonstrating the

need for proper data coverage and processing to avoid misinterpretations

4.2 Knowledge gaps and limitations

This project, CHPM2030, requires the prediction of structures and lithologies in complex environments at

depth down to 7 km. Predicting fracture geometry and permeability at depth in the crystalline bedrock is a

crucial point as well and highly challenging. With the present knowledge and data availability this task is not

easily to fulfill. For pilot areas within CHPM2030, further intensive multi-disciplinary studies must be

considered, e.g., three-dimensional electromagnetic and seismic surveys, as well as better predictions of

temperature, heat flow and permeability at depth. The 3D integration of geological and geophysical results

will then better allow for planning and conducting of exploration and possibly later-on production drillings.


(A1.2.4) 32 / 49

5 Concluding remarks

Mineral deposits in Sweden that may have bearing on the present task are those that originally formed at

some depth in the crust as they may represent fossil analogues to ongoing processes. Examples of such

mineralisations are Tallberg, Aitik, Nautanen, Yxsjöberg, Pingstaberg, Bastnäs, Harnäs and Laisvall. The

apatite-bearing iron deposits of Kiruna-type may also be relevant. The generally low geothermal gradient

being less than 20 oC/km in the crystalline basement of the Fennoscandian Shield in Sweden (Eliasson et al.

1991) will allow for low- to mid-enthalpy geothermal systems as part of a possible CHPM unit.

6 Acknowledgements

We thank our colleagues at SGU, Uppsala and Luleå universities and mining companies for valuable input to

this report. Mikael Erlström is thanked for critical reading the manuscript.

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8 Appendix

Figure A.1. Map of the anomalous total magnetic field over Sweden derived from airborne magnetic

measurements (SGU 2016). Typical distance between flight lines is 200 m, measuring altitude either, 30 or

60 m, with data points along flight pass every 17 m.

Figure A.2. Coverage of Sweden by airborne very low frequency (VLF) measurements (SGU 2016). Areas in

colour where electrical resistivity of the uppermost surface could be obtained while data of areas in grey

represent older data not being methodologically applicable for deriving resistivity.

Figure A.3. Map of Sweden with areas where airborne measurements of natural gamma radiation were done

(SGU 2016). Shown here is the concentration of uranium (238 U in ppm) in the uppermost soil and bedrock

of the Earth. The other two isotope elements observed are potassium and thorium making it possible, e.g.,

to identify bedrock units close to the surface and calculate their heat production rate.

Figure A.4. Gravity anomaly map (Bouguer anomaly in mGal) of Sweden (SGU 2016) based on the SGU

database with contributions from third parties. Measuring sites account to about 183000, with gridding of

data done for areas of 500 x 500 m2.

Table A.1. Summary of databases held by SGU and relevant for the CHPM2030 project.

Table A.2. Summary of data in web map services (WMS) – as from the Map Viewer, held by SGU and relevant

for CHPM2030. In accordance with INSPIRE access is free of charge.

http://pure.ltu.se/portal/en/persons/par-weihed(801d336e-43e8-44a9-9526-0d2546ad1ae7).html

http://pure.ltu.se/portal/en/publications/a-review-of-palaeoproterozoic-intrusive-hosted-cuaufeoxide-deposits-in-northern-sweden(f0a2aeb0-f486-11db-ac9f-000ea68e967b).html

http://pure.ltu.se/portal/en/publications/a-review-of-palaeoproterozoic-intrusive-hosted-cuaufeoxide-deposits-in-northern-sweden(f0a2aeb0-f486-11db-ac9f-000ea68e967b).html


(A1.2.4) 43 / 49

Figure A1.


(A1.2.4) 44 / 49

Figure A.2.


(A1.2.4) 45 / 49

Figure A.3.


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Figure A.4.


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Datasets Short description Scale Coverage Access cost Link Source/Contact [email protected]

Access cost http://www.sgu.se/produkter/kundtjanst/avgifter-for-sgus-material/ (in Swedish). Remark: Data covered by INSPIRE or for scientific research are free of charge.

Bedrock, Mineral Resources

Dating, isotope analysis See web

Drill cores

Bedrock, observations

Drill cores Drill core archive c. 18000 cores, c. 3000000 m

Drill cores, hyperspectral scanning, IR data

Drill core archive 233 000 m (Sept 2016)

Quaternary geology

Quaternary deposits different scales

Sedimentary thickness

Hydrogeology

Groundwater

Wells

Geochemistry

Biogeochemistry

Soil geochemistry

Geophysics

Gravity Land, sea based and airborne point data, grid 500 x 500 m2

c. 186000 measuring sites

See web-page

Magnetic Field

Airborne total magnetic field data, Profile density mostly 200 m, data points every 18 m.

Grid data 200 by 200 m, 200 by 40 m, or less.

Gamma radiation Airborne survey data for the radioactive isotopes U, K and Th.

Grid resolution as above.

ElectromagneticField

Airborne Very Low Frequency (VLF) data. Slingram data partly available.

Grid data 200 by 18 meters.

Petrophysics Density and magnetic properties of rocks. Content of U, K, Th..

c. 75000 samples. 5900 outcrop data.

Table A.1.


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Datasets Short description Scale Cove-

rage

Access

cost Link

Source/Contact

Web map services (datasets):

http://www.sgu.se/en/products/data/data-in-web-map-services-wms/

Maps: http://apps.sgu.se/kartgenerator/maporder_en.html;

http://www.sgu.se/en/products/maps/map-viewer/

Access cost These datasets are covered by INSPIRE and free of charge.

Bedrock, ores and minerals

Bedrock 1:1 M See above See

above

Drill cores

Ores and mineralizations

Mineral resources

Mineral permits

Mineral deposits of national

interest

Groundwater, wells and groundwater monitoring

Wells

Groundwater 1:1 M Sweden

Environmental monitoring

Springs

Geophysics

Geophysical ground

measurements, prospecting

areas

Airborne geophysics, magnetic

field

Airborne survey data

showing variation in

the total magnetic

field.

Airborne geophysics, gamma

radiation uranium, potassium,

thorium


for the radioactive

isotopes U, K and Th.

Resolution

information

on website

http://apps.sgu.se/kartgenerator/maporder_en.html


(A1.2.4) 49 / 49

Footnote: * Other scales available (e.g., 1:200000; 1:250000; 1:750000).

Table A.2.

Datasets Short description Scale Cove-

rage

Access

cost Link

Geophysical ground

measurements, gravity


showing variation in

the magnetic field.

Resolution

information

on website

Geochemistry

Biogeochemistry, copper

Ground geochemistry, copper

Quaternary deposits

Ground stability properties free

Ground permeability free

Quaternary deposits At scales from 1:25000

to 1:1 M* free

Landslides and gullies free


REPORT ON DATA COLLECTION

BY THE EFG LINKED THIRD PARTIES

(EUROPEAN DATA INTEGRATION AND EVALUATION)

Authors:

Vanja Bisevac, Isabel Fernandez (European Federation of Geologists)


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Table of contents 1 Executive summary .......................................................................................................................... 4

2 Introduction and the scope of the survey ........................................................................................ 5

3 European outlook ............................................................................................................................ 6

3.1 Survey data overview ............................................................................................................... 6

3.2 Availability of the data and number of the drill holes per country .......................................... 8

3.2.1 AUSTRIA ........................................................................................................................... 8

3.2.2 BELGIUM .......................................................................................................................... 8

3.2.3 CROATIA ........................................................................................................................... 9

3.2.4 GERMANY ........................................................................................................................ 9

3.2.5 GREECE ............................................................................................................................ 9

3.2.6 HUNGARY ....................................................................................................................... 10

3.2.7 IRELAND ......................................................................................................................... 10

3.2.8 ITALY .............................................................................................................................. 10

3.2.9 LUXEMBOURG ............................................................................................................... 10

3.2.10 NETHERLANDS ............................................................................................................... 11

3.2.11 POLAND ......................................................................................................................... 11

3.2.12 PORTUGAL ..................................................................................................................... 11

3.2.13 SERBIA ............................................................................................................................ 11

3.2.14 SLOVAK REPUBLIK .......................................................................................................... 11

3.2.15 SLOVENIA ....................................................................................................................... 11

3.2.16 SPAIN ............................................................................................................................. 12

3.2.17 SWEDEN ......................................................................................................................... 12

3.2.18 SWITZERLAND ................................................................................................................ 12

3.2.19 UNITED KINGDOM ......................................................................................................... 12

3.3 Identification of the metal enrichment .................................................................................. 13

3.3.1 AUSTRIA ......................................................................................................................... 13

3.3.2 BELGIUM ........................................................................................................................ 13

3.3.3 CYPRUS .......................................................................................................................... 14

3.3.4 HUNGARY ....................................................................................................................... 14

3.3.5 POLAND ......................................................................................................................... 15

3.3.6 SERBIA ............................................................................................................................ 18

3.3.7 SLOVAK REPUBLIC .......................................................................................................... 21

4 Conclusions .................................................................................................................................... 23

5 References ..................................................................................................................................... 23

5.1.1 BELGIUM ........................................................................................................................ 23

5.1.2 CYPRUS .......................................................................................................................... 24

5.1.3 GREECE .......................................................................................................................... 24

5.1.4 HUNGARY ....................................................................................................................... 24

5.1.5 LUXEMBOURG ............................................................................................................... 24

5.1.6 POLAND ......................................................................................................................... 24

5.1.7 PORTUGAL ..................................................................................................................... 25

5.1.8 SERBIA ............................................................................................................................ 25

5.1.9 SLOVAK REPUBLIK .......................................................................................................... 25

5.1.10 SLOVENIA ....................................................................................................................... 26

5.1.11 UK .................................................................................................................................. 26


(A1.2.5) 3 / 30

6 Appendix 1. LTPs contact list: ........................................................................................................ 28

7 Appendix 2. Template for data collection by the EFG Linked third Parties in the frame of Task

1.2.5 - European data integration and evaluation CHPM2030, Work-package 1 - Methodology

framework definition ..................................................................................................................... 29

7.1 Background ............................................................................................................................ 29

7.2 Data on drilling programmes ................................................................................................. 30

7.3 Data on deep metal enrichments .......................................................................................... 30

7.4 Personal data ......................................................................................................................... 31

List of tables

Table 1. Data Overview: Please note that some of the LTPs reported also on metal enrichments which

do not satisfy the CHPM2030 criteria. See text for further explanations. y – yes; n - no

Table 2. List of Belgian deep wells crossing the 100°C isotherm depths. Balmatt-2 is not incorporated

since the drilling is still in progress. The wells of both St-Ghislain and Havalange have partially been

closed. * Temperature extrapolated from 105°C at 2155 m to the depth of 2195 m

List of figures

Figure 1. Distribution of the drillholes in Slovenia


(A1.2.5) 4 / 30

1 Executive summary

The information reported here has been obtained by reviewing information from 24 European

Countries reporting by the European Federation of Geologists, EFG, Linked Third Parties, LTPs. EFG

LTPs collected publicly available data at national level on deep drilling programs, geophysical and

geochemical explorations and any kind of geo-scientific data related to the potential deep metal

enrichments. The task provides a “European outlook” on data availability in order to identify data

gaps. In this survey we used the term “metal enrichment” considering the geological formations in

which the metal content is at least five times higher than the average in the given formation type.

This term also includes the “real ore bodies” which have economic value on their own. The LTPs were

asked to consider the following metals: Cu, Zn, Pb, Fe, As, Sb, Ag, Au, Co, Cr, Ni, U, Sn, W and Mo, but

were also invited to report on any other metal enrichment they find important and relevant in their

countries.

The 19 countries out of 23 which participated in this survey reported that drillholes with temperatures

exceeding 100°C exists in their country (Table 1). The number of such drillholes varies from 1 (Ireland)

to 2809 (Germany) (Table 1). The data are publicly available for drillholes in Belgium, Greece,

Netherlands, Poland and Portugal, while only partly available in Austria, Hungary, Ireland, Serbia,

Slovenia, Spain, Sweden and UK. Unfortunately, the drillholes data are not publicly available in Croatia,

Germany and Switzerland. The Czech Republic, Finland and Luxembourg did not report the existence

of the drillholes with temperatures exceeding 100°C and are not considered in further discussion.

Among them, eight countries mentioned the identification of metal enrichment (Austria, Belgium,

Cyprus, Hungary, Poland, Serbia, Slovak Republic and UK, while five of those (Belgium, Hungary,

Poland, Serbia and Slovak Republic) provided more detailed insight into these metal enrichments

providing some data on geographical, geological, geochemical and geophysical data. These countries

could be of further interest of the CHPM2030 interest. Since the data of the project’s interest only

partly publicly available or not available at all, further cooperation with National experts and possible

contact to organizations in charge/owning the data will be necessary to obtain all relevant

information.


(A1.2.5) 5 / 30

2 Introduction and the scope of the survey

Since the objective of CHPM2030 WP1 is to prepare the conceptual framework for a novel enhanced

geothermal system (EGS) for the production of energy and the extraction of metals from ore deposits

located at great depths, first step was to synthesize our knowledge on deep metal enrichments that

could be converted into an “orebody EGS”, and to investigate the characteristics of these bodies. We

aimed to discover and examine the geological, tectonic, geochemical, and petrologic factors that

define the boundary conditions of such novel EGS both in terms of energy and potential for metal

recovery.

The information reported here has been obtained by reviewing past investigations in Europe that have

resulted in public access geological and geothermal datasets. In addition to these data, associated

publications and studies have been also reviewed. EFG Linked Third Parties collected publicly available

data at national level on deep drilling programs, geophysical and geochemical explorations and any

kind of geo-scientific data related to the potential deep metal enrichments. They also collected data

on the national geothermal potential. The task provides a “European outlook” on data availability in

order to identify data gaps. A horizontal task is to connect two insofar unconnected communities:

mining and geothermal earth science professionals for a common goal on EU and national levels. In

the third year of the project implementation, within WP6 – Roadmapping and Preparation for Pilots,

the EFG Linked Third Parties will assess the geological data on suitable ore-bearing formations and

geothermal projects, which were collected in this Survey, in relation with the potential application of

the CHPM technology.


(A1.2.5) 6 / 30

3 European outlook

As we want to apply an EGS system, in the data collection we were looking for the depths where the

temperature is above 100°C. The TLPs were asked to use the average geothermal gradient in their

country and during the data collection to consider only drillholes which reached at least this depth. If

such drillholes are available, LTPs were asked to provide the number of the drillholes, availability of

the data, to specify the metal enrichment in such drillholes if identified.

For each metal enrichment they were asked to provide additional and specific information, if available,

such as:

a) Geographical data of metal enrichment (metal, locality, coordinates)

b) The depth in meters where the metal bearing formation was reached

c) The extent of the metal enrichment known in the sense of width, length and height

d) To specify many drillholes identified the given metal enrichment

e) The geological data from the metal enrichment regarding stratigraphy, lithology and structure

f) The geochemical data - rock chemistry and fluid chemistry

g) The geophysical data - Normal resistivity logs, Fluid resistivity logs, Spontaneous-potential

logs, Acoustic logs and Gamma logs together with information on any other surface or

airborne geophysical surveys which provide additional data related to the metal enrichment.

Additionally, LTPs were asked to provide the list of references for the data they specified together with

any other remark they considered important for this data collection.

3.1 Survey data overview

The Table 1 shows the data overview collected during the survey with some basic information on data

on drilling programs and detected metal enrichment.

Note that some of the LTPs reported also on metal enrichments which do not satisfy the CHPM2030

criteria.


(A1.2.5) 7 / 30

Table 1. Data collection overview

DATA ON DRILLING PROGRAMMES METAL ENRICHMENT(S)

Country

Drillholes with

temperatures

exceeding 100°C

reported (y/n)

Number of

such

drillholes

Data from

drillholes

publicly available

(y/n)

Identified

(y/n)

Reported

(y/n)

Elements

reported

Austria y ca. 100 y, partly y n Ni

Belgium y 4 y y y Cu, Pb, Zn,

U, Th

Croatia y ca. 1000 n n n -

Czech

Republic n - - - - -

Cyprus n - - y n Cu

Finland n - - - - -

Germany y 2809 n - - -

Greece y 5 y n n -

Hungary y 100 y, partly y y Cu, Zn, Pb,

Ireland y 1 y, partly n n -

Italy y 694 y n n -

Luxembourg n - - - - -

Netherlands y >800 y n n -

Poland y a few

dozens y y y

Cu, Ag, Au,

Pt-Pd, Se,

Pb, Zn, Mo,

V, Ni, Co,

W, Bi, Ag,

Te, Ni

Portugal y min 18 y n n -

Serbia y min 3 y, partly y y Cu, Au

Slovak

Republic y 3 y y y

Fe, Cu, Mo,

Bi, Pb, Zn,

Au, Ag, Te,

Sb, Hg, and

As

Slovenia y 41 y, partly n n -

Spain y 33 y, partly n n -

Sweden y 3 y, partly n n -

Switzerland y 2 n n n -

Ukraine n - - - - -

UK y 27 y, partly y y Sn, W, Cu,

Li, Rb, Cs


(A1.2.5) 8 / 30

3.2 Availability of the data and number of the drill holes per country

The 19 countries out of 23 which participated in this survey reported that drillholes with temperatures

exceeding 100°C exists in their country (Table 1). The number of such drillholes varies from 1 (Ireland)

to 2809 (Germany) (Table 1). The data are publicly available for drillholes in Belgium, Greece,

Netherlands, Poland and Portugal, while only partly available in Austria, Hungary, Ireland, Serbia,

Slovenia, Spain, Sweden and UK. Unfortunately, the drillholes data are not publicly available in Croatia,

Germany and Switzerland.

Please find below the detailed overview per country (listed alphabetically) from the 19 countries

which reported existence of drillholes with temperatures exceeding 100°C. Countries which provided

additional data which could be of the project interest are also mentioned in this section. The Czech

Republic, Finland and Luxembourg did not report the existence of the drillholes with temperatures

exceeding 100°C and are not considered in further discussion, if not stated otherwise.

3.2.1 AUSTRIA

According to the available data, Austria could have a large geothermal potential throughout its’ deep

(alkali) metal enrichment zones. The Geological Survey of Austria reported that around 100 drilling

programmes reached the +100°C isotherm of which some with known Ni-enriched reservoir(s) (P.C.

Gregor Goetzl, 2016).

Nevertheless, most of the data requested is not or only partly publicly available since most of the

hydro chemical datasets related to deep aquifers are obtained by the hydrocarbon industry.

Interesting to note is an ongoing research on scaling and erosion at thermal wells in Austria with focus

on geochemical components in deep reservoirs. More information on this could be obtained from the

contact if project consortium decides it is necessary.

3.2.2 BELGIUM

Judging from the data received Belgium could be of CHPM2030 interest. 5 wells reached the 100°C

isotherm depth, in the Table 2 information about 4 wells is presented: Balmatt-1, Havelange, St-

Ghislain and Turnhout. The 5 well is Balmatt-2, not incorporated since the drilling is still in progress.

The Balmatt-1 and Balmmatt-2 wells were drilled for hydrothermal energy exploration (VITO).

Both Havelange and St-Ghislain wells have been sealed at certain depth some time ago. Nevertheless,

reopening of the Havelange well is being considered at the moment. According to geothermal maps

and several temperature logs in deep wells, a temperature of +90°C is found at 2000 m depths in the

northeast of the Campine Basin.

Wells location Depth

(m)

temp gradient

(°C/Km)

Temp (°C) Stratigraphy

Balmatt-1 Mol 3600 35.5 138 Lower-Carboniferous

168W314 Havelange 5648 18.6 115 Mississipian, upper Dev.

150E387 St-Ghislain 5403 30.5 175 Mississipian, upper Dev.

29E144* Turnhout 2195 47.8 115* Lower-Carboniferous

Table 2. List of Belgian deep wells crossing the 100°C isotherm depths


(A1.2.5) 9 / 30

3.2.3 CROATIA

Geothermal gradient in Croatia varies significantly between the Dinarides (av. 18°C/km) and the

Pannonian basin (av. 49°C/km). Around 1000 boreholes have a depth greater than 2000 m in Croatia,

but an exact number has not been provided. Those wells, lying in the Pannonian Basin, should reach

around 100°C. However, some of these past drilled wells have been sealed off (P.C. Borovic S., 2016).

Data on deep metal enrichments may exist but are not listed in databases, not examined or have not

been made publicly available.

In Croatia, mostly in period from the 1950s until 1990s, thousands of boreholes were drilled in the

scope of hydrocarbon prospection, mostly in the Pannonian part of Croatia and northern Adriatic by a

public petroleum company INA. INA was later partially privatized and data became unavailable.

Nevertheless, some years ago the Ministry of Economy took charge of this data, which are now in the

ownership of the Ministry. All data is physically placed at HGI-CGS (Croatian Geological Survey). Data

availability will be regulated by a special regulation issued by the same Ministry. However, the Ministry

did not issue the regulation so the data is until now unavailable and, even if data were fully accessible,

it is in a form of scanned reports from 1950s onwards. Only manual scanning and analyzing is possible

on this data since no further digitalization and creation of comprehensive database has been

performed, which means a very time-consuming activity. Moreover, data about metal enrichment

zones would be extremely rare in the reports (P.C. Borovic S., 2016).

3.2.4 GERMANY

The 2809 drillholes which reached the depths where the temperature exceeds 100°C has been

identified in Germany, although there is not publicly available date for those drillholes, as reported. At

the moment, Germany should be considered as potential interest of the CHPM2030, although

different approach should be used to obtain desired data.

3.2.5 GREECE

The 5 drillholes which reached the depths where the temperature exceeds 100°C were identified in

Greece, but no metal enrichment has been identified. Despite that fact, additional data related to

drillholes were provided and listed below.

Drillhole 1: WGS84 coordinates: Ε24.448737 Ν36.735608 - The drillhole has a 1163 m total depth and

the temperature reached 308°C.

Stratigraphy: The topmost horizons of the stratigraphy are tuffs reaching a depth of 107 m

followed by an 8 meter thick green lahar. The succession continuous with altered calcite tuffs.

Another interbedded green lahar horizon appears in a depth of 470 m and the series continues

with altered tuffs associated with anhydrite, calcite and pyrite. A 707 m bellow surface, a 50

meter characteristic horizon of Neogene limestone is present and then follows the

stratigraphically lowermost part which is the metamorphic crystalline basement.

Drillhole 2: WGS84 coordinates: E24.487253 N36.704649 - The total drillhole depth is 1101 m and the

higher measured temperature was 310°C.

Stratigraphy: The drillhole initially penetrates alluvial deposits and then in a depth of 100 m

reaches a green lahar volcanic rock. 60 m bellow, there are alternations of silicified and kaolinitic

tuffs. In a depth of 260 m, a series of low-grade schists appears to form the basement in the area,

whereas, the deeper part appears to be layered by sericite chlorite schists with quartz.


(A1.2.5) 10 / 30

Drillhole 3: WGS84 coordinates: E24.50093 N36.710754 - The drillhole is 1017 m deep and the

temperature of the surrounding rocks exceeded 250°C.

Stratigraphy: A relatively thin layer of green lahar is underlain by 100 m of altered volcanic rocks.

The succession continuous with Neogene sediments. The 172 m below the surface is the contact

with the low-grade metamorphic basement.

Drillhole 4: WGS84 coordinates: E27.172702 N36.581755 - The total borehole depth is 1800 m and the

temperature exceeds 350°C.

Stratigraphy: The borehole penetrates series of volcanic rocks comprising basaltic andesite,

andesite, dacite to trachydacite and rhyolites, associated with different phases of past volcanic

eruptions.

Drillhole 5: WGS84 coordinates: E24.622379 N40.956164 - The drillhole has a depth of 1377 m and

the rock temperature reaches 122°C.

Stratigraphy: The 250 m of mainly deltaic sediments are followed by 300 m of impermeable

marly-argillaceous Pliocene sediments. The succession continuous with a transitional

sedimentary zone of calcarenites and oolithic limestones. In a depth of 690 m, a basal

conglomerate and breccia appears. A lower amphibolitic series and schists with marble

intercalations forms the lowermost lithologies.

3.2.6 HUNGARY

Around 100 drillholes, which reached the depths where the temperature exceeds 100°C, were

identified in Hungary. For more than 10 of them the data, which could be useful for the future actions

of the project, are publicly available via database of National Office of Mining and Geology, in

concession database of Oil researches. Unfortunately, no metal enrichment important for the scope of

projects was identified below the depths where the temperature exceeds 100°C. Nevertheless, the

other metal enrichments were reported (see 3.3. for detail explanation).

3.2.7 IRELAND

One drillhole which reached the depths where the temperature exceeds 100°C was identified in

Ireland. It was drilled in 1965 for hydrocarbon exploration with no mineral enrichment noted. The data

from the drillhole is only partly publicly available. Additionally, there is regional geophysical data

(magnetics, radiometrics and EM) for approximately one third of the country available on

www.tellus.ie

3.2.8 ITALY

Exact 694 drillholes, which reached the depths where the temperature exceeds 100°C, were identified

in Italy managed by the Ministry of Economic Development in the frame of "Geothermal Resources

National Inventory". The inventory comprise data for 948 geothermal wells (the first one was drilled in

1900 and the last one being drilled yet). At the moment the 268 are free for consultation. Among all

the geothermal wells included in the inventory, 694 of them can be distinguished as those with

T > 100°C. Unfortunately, none of the geothermal wells provide any metal enrichment information.

3.2.9 LUXEMBOURG

According to the information obtained from the Service Géologique du Luxembourg, no drillholes

which reached the depths where the temperature exceeds 100°C exists neither metal enrichment


(A1.2.5) 11 / 30

were identified below the depths where the temperature exceeds 100°C. The deepest well has a

depth of +700 m with a bottom temperature of 25°C.

Schintgen (2015) expects temperatures of +90°C to around 120°C at depths of respectively 3.5 km to 5

km based on 2D models. Quartzite-rich Lochkovian deposits, near the western Eifel region in

Luxembourg, could prospectively enable combined geothermal heat production and power

generation.

3.2.10 NETHERLANDS

More than 800 drillholes, mostly drilled for the purposes of oil/gas industry, which reached the depths

where the temperature exceeds 100°C has been identified in Netherlands. There are data publicly

available for each drillhole (www.nlog.nl). No metal enrichment has been identified below the depths

where the temperature exceeds 100°C. Most of the data about the subsurface is freely available via

various web portals with regards to subsurface models, drillhole descriptions and geothermal

potential like www.thermogis.nl, www.nlog.nl and www.dinoloket.nl.

3.2.11 POLAND

A few dozen of drillholes which reached the depths where the temperature exceeds 100°C were

identified in Poland with publicly available data and metal enrichment identified (see 3.3. for detail

explanation).

3.2.12 PORTUGAL

The 8 drillholes in Continental Portugal and at least 10 geothermal wells in Azores were reported

which reached the depths where the temperature exceeds 100°C. The data are publicly available for 8

drillholes. The metal enrichment below the depths where the temperature exceeds 100°C was not

identified.

3.2.13 SERBIA


Serbia. A few more (5) are close to this temperature, and will be probably reached if drilling go deeper.

For 4 of these drillholes the data are publicly available and metal enrichment identified (see 3.3. for

detail explanation).

3.2.14 SLOVAK REPUBLIK

Total of 3 drillholes which reached the depths where the temperature exceeds 100°C together with

metal enrichment identified below the depths where the temperature exceeds 100°C were identified

in Slovak Republic. Data for all 3 drillholes are publicly available (see 3.3. for detail explanation).

3.2.15 SLOVENIA

Total of 41 drillholes reached the depths where the temperature exceeds 100°C exists in Slovenia

(+additional 24 drillholes where 100°C would be reached certainly if measured) All drillholes in

Slovenia in which temperature exceeds 100°C belongs to exploration oil & gas drillholes, drilled in

Tertiary sediments and its basement in the eastern part of Pannonian basin.

Most of data from these drillholes are not public available, but many data were published in the scope

of EU funded projects T-JAM and TRANSENERGY. The data is available on internet: akvamarin.geo-

zs.si/t-jam_boreholes/ and www.arcgis.com/home/webmap/viewer.html?

webmap=f82fe0f737174219a354f4209ea7448a&extent=12.1518,45.3238,20.2487,49.1158.

http://akvamarin.geo-zs.si/t-jam_boreholes/

http://akvamarin.geo-zs.si/t-jam_boreholes/

http://www.arcgis.com/home/webmap/viewer.html?webmap=f82fe0f737174219a354f4209ea7448a&extent=12.1518,45.3238,20.2487,49.1158

http://www.arcgis.com/home/webmap/viewer.html?webmap=f82fe0f737174219a354f4209ea7448a&extent=12.1518,45.3238,20.2487,49.1158


(A1.2.5) 12 / 30

There is currently neither one drillhole in Slovenia where metal enrichment would be found and which

exceeds 100°C. The problem is that large part of Slovenian territory is not investigated deeper than

500 m yet as is seen from the figures below.

Figure 1. Distribution of the drillholes in Slovenia

3.2.16 SPAIN


Spain. For 8 of them the data are publicly available. The metal enrichment below the depths where

the temperature exceeds 100°C were not identified.

3.2.17 SWEDEN

As an active partner of the CHPM2030 project and coordinator of taskforce 1.2 in WP1 the Geological

Survey of Sweden will deliver a full report on the Swedish CHPM potential in taskforce 1.2.4.

Information given here is thus very briefly. Sweden has 3 deep cores crossing the 100°C isotherm

(Räby (Skania) 3702 m, Gravberg (Siljan) 6957 m and Stenberg (Siljan) 6529 m). Unfortunately, no

deep metal enrichment zones have been identified. Data of these drillholes are partially public

available.

3.2.18 SWITZERLAND

The two drillholes which reached the depths where the temperature exceeds 100°C were identified in

Switzerland with no mineral enrichment identified. Unfortunately,, both projects (Basel and St Gall)

are are abandoned and the data from these drillholes are not publicly available at this moment.

3.2.19 UNITED KINGDOM

The UK and British Geological Survey is an active partner of the CHPM2030 project and will analyze

several samples. A full report on the potential of the UK is most likely published during the next

project years.

At least 27 offshore North Sea hydrocarbon fields where temperatures exceed 100°C have been drilled

with multiple wells per field, and some with 10s of wells. Data is partly available. Since these are

hydrocarbon wells, older ones have more openly available information, but newer well may still be

under restricted access. Geochemical data points out that some sulphide minerals are present

(reducing circumstance of hydrocarbons). Nevertheless, no economic metallic mineralization is noted

or expected.

Boreholes deeper than 1 km Boreholes deeper than 2 km


(A1.2.5) 13 / 30

Deep onshore wells exist, e.g. Rosemanowes site with a 2180, 2350 and 2800 km deep well) but

bottom hole temperatures do not reach the CHPM restrictions. Above mentioned cores were part of a

Hot Dry Rock (HDR) geothermal project from the 1970s to the 1990s in southwest England (see HDR-

references). One well is still available for bottom hole testing. The HDR potential of southwest England

originates from several granite batholiths and intrusions (e.g. Cam Brea granite and Cammenellis

granite).

The Cornubian orefield, or other orebodies in SW England (Cornwall, Devon & part of Somerset), are

related to high heat productivity and stress history of these granite batholiths. The whole region is

enriched with a variety of metals, the primary ones of which occur in zones around bodies of granite.

Typically initial (higher temperature) mineralization consisted of Sn, W (± others). This was followed by

later (i.e. lower temperature) precipitation of Cu (± others), and finally at even lower temperatures Zn,

Pb (± others). Locally, enrichment is generally concentrated within 500m of the contact between

granite and surrounding sediments. Such ore deposits are mined until depths up to 790m (South

Crofty deep mine) and consist almost certain at depths reaching 100°C (BGR). Since the metals are

mineralized in fractures of thermally metamorphosed Devonian mudstones, no estimation of the real

size of this ore body at such depths is available.

Borehole measurements, geophysical logs and geophysical airborn data (TELLUS-project, 2013) can be

consulted at GSB or in several HDR reports. Underground observations in South Crofty deep mine

(790m) by Bromley and Thomas (1988), summarized in Smedley et al. (1989), suggested the presence

of intermediate salinity circulating water in crosscourse fractures and veins, distinct from high salinity

waters trapped in cavities along the lodes. ongoing alteration phenomena associated with the

circulation of warm saline water (up to 45°C) is observed. Here the brine consists of iron oxy-

hydroxides and calcium silicate (Thomas and Milodowski, 1988). Hydrogeochemical analysis of the

shallow groundwater’s of the Cammenellis granite prove the presence of trace alkali metals Li, Rb an

Cs (Smedley 1989) but no mention is made of the exact quantity of these alkali metals. Even so, the

granite batholith may have caused some alkali metal enrichments, true ore deposits caused by

hydrothermal fluid flow linked with these granites are of a bigger importance for CHPM.

3.3 Identification of the metal enrichment

Eight countries mentioned the identification of metal enrichment: Austria, Belgium, Cyprus, Hungary,

Poland, Serbia, Slovak Republic and UK, while five of them (Belgium, Hungary, Poland, Serbia and

Slovak Republic) provided more detailed insight into these metal enrichments providing some data on

geographical, geological, geochemical and geophysical data. See further text for more details,

countries listed alphabetically).

3.3.1 AUSTRIA

Although Austria possesses a large number of wells crossing the 100°C isotherm little data on deep

metal enrichment zones is publicly available, apart from the occurrence of interesting amounts of Ni in

some deep aquifers. No details were provided on those aquifers.

3.3.2 BELGIUM

The two metal enrichment zones, with a hypothetical occurrence around depths reaching 100°C or

more, are expected in some areas:

1. The U and Th enriched Chokier and Souvré Formations occur in the Campine Basin, Liege Basin

and Mons Basin. Only the most north-eastern part of the Campine Basin has modelled Chokier


(A1.2.5) 14 / 30

and Souvré depths reaching up to 5000 m, thus crossing the +100°C isotherm. The U and Th

enrichments have been measured during logging and reached respectively 18 and 17 ppm. Both

formations consist of shales deposits of Visean-Serpukhovian age. The thickness of the combined

formations increases towards 100 m thick in this north-eastern Campine area. Nevertheless, it

should be noted that thick underlying Under-Carboniferous carbonate aquifers are a target for

deep geothermal energy, geological storage of natural gas and CO2 and the Chokier and Souvré

Formation are a possible target for unconventional extraction of shale gas.

2. A mineralized fault systems comprising Cu-Pb-Zn sulphide type hydrothermal deposits with minor

Au and Ag in central to NW Belgium. The enrichments have been identified in several drillholes

going up to 400 m depth (St-Pieters-Kapelle wells). Low-angle and high-angle faults have been

tracked by aeromagnetic prospection and faults dip towards the northeast. The existing steep

dipping mineralized faults are thought to cross the 100°C isotherm. Pyrite veinlets and quartz

mineralized veins have at measured depths maximum 0.25, 0.25 and 1.6 wt% of Cu, Pb and Zn in

the cored low-angle faults. The degree of ore mineralization might increase at greater depths.

More information about the two metal enrichments on stratigraphy, lithology, structure and

geochemical data could be provide if it is required by CHPM2030.

3.3.3 CYPRUS

Although, no drillholes which reached the depths where the temperature exceeds 100°C exists neither

any metal enrichment were identified below the depths where the temperature exceeds 100°C on

Cyprus, some general information on metal enrichment were collected.

Regarding Cu and associated Ag and Au, the massive sulphide deposits (Cyprus type) are very well

known how they are formed. They are located between the upper and lower pillow lava horizons and

all on or near the surface deposits have been explored and extensively exploited since antiquity. In

fact, the mining wastes of the past are currently exploited with the recovery of Cu from wastes with

concentration of Cu as low as 0.1% by using hydrometallurgy. In addition to this, in-situ leaching is also

carried out in ore deposits with concentration of Cu as low as 0.05%.

Please note that the Cyprus Crustal Study Project run in 1984 and Geological Survey Department (GSD)

was involved. Its’ framework included deep borehole drilling in different places in Europe. In Cyprus,

five deep boreholes were drilled at the Ophiolite near Palaichori, Mitsero, Ayio Epiphanio and Klirou

(two boreholes) with 2263 m, 701 m, 689 m, 485 m and 226 m depth respectively. Finally, a large

number of parameters were measured like Resistivity and Temperature.

3.3.4 HUNGARY

The Cu, Zn, Pb with a few Ag and Au polymetallic metal enrichment in shallow hydrothermal dykes:

160–400 m, skarn type polymetallic ores in 600–1100 m depth (Recsk, Hungary; 47°55'48.9"N

20°04'55.5"E). The estimated width and length of the body is more than 500 m while height is about

200–600 m with separated dykes. This metal enrichment was identified by more than 100 drillholes.

Geological data:

Triassic limestone over burned by Eocene andesitic subvolcanic material. The documentation is in

manuscript in National Archive of Mining, Geology and Geophysics in Budapest.

a) Stratigraphy - Shallow ore deposit: Eocene andesitic dykes, skarn deposits: Triassic limestones,

silicified

b) Lithology - Andesitic dykes and silicified limestones


(A1.2.5) 15 / 30

c) Structure - Complicate, as a subvolcanic body

Geochemical data:

It was measured, published in nationwide and international periodics. The last summary is in a

manuscript made by Hungarian Geological Institute (Scharek 2004).

Geophysical data:

Drillhole geophysics during the geological investigation. Data are in National Archive of Mining,

Geology and Geophysics, Budapest. Normal resistivity logs as well as Spontaneous-potential and

Gamma logs are available for all drill holes. Additional data related to the possible metal enrichment

are in Helsinki, Finland.

3.3.5 POLAND

In a few drillholes in SW Poland (Foresudetic Monocline): Cu-Ag mineralization, 100°C at the depth ca.

2500-3000 m, drillholes depth 2430–3860 m, geothermal degree 28-33 m/1°C, e.g. drillholes: Mozów

(2537 m), Wilcze (2432 m), Paproć (2609 m), Kaleje (3136 m), Żerków (3548 m), Florentyna (3865 m)

the metal enrichment has been identified below the depths where the temperature exceeds 100°C.

METAL ENRICHMENT 1:

Copper-silver ore of the stratiform type, a dozen occurrences in the Foresudetic Monocline, from

western border of Poland to SE part of Wielkopolskie voivodeship on the different depths 900–3700 m

at lower Zechstein Kupferschiefer ore series. All occurrences are divided on two group, first to the

depth 2000 m and second on the depth below 2000 m. The extent of the metal enrichment is known

as follows:

First group of the occurrences - up to depth 2000 m:

1. KULÓW - prognostic area 132 km2, depth 1500-2000 m in 8 wells

2. LUBOSZYCE - prognostic area 91 km2, depth 17460-1550m in 7 wells

3. ŚCINAWA WEST - prognostic area 16 km2, depth1200-1368 in 4 wells

4. ŚCINAWA NE - perspective area 25 km2, depth 1338 at 1 well

5. BORZĘCIN - perspective area 9 km2, depth 1496m in 1 well

6. MIRKÓW - perspective area 35 km2, depth 1176 m in 1 well

7. ŚLUBÓW - perspective area 25 km2, depth 1384m in 1 well

8. ŻARKÓW - perspective area 9km2, depth 1359 m in 1 well

9. CZEKLIN - hypothetical area 31 km2, depth 1733m, 1 well

10. HENRYKOWICE – hypothetical area 17 km2, depth 1466-1602,5m 4 wells

11. JANOWO - hypothetical area 50km2, depth 1712,7m in 1well

12. MILICZ - hypothetical area 15 km2, depth 1646,6m in 1 well

13. SULMIERZYCE - hypothetical area 261 km2, depth 1580,2-1909,1m in 4 wells

14. WARTOWICE WEST - prognostic area 6 km2, depth 941,3-1463,0 m in 4 wells

Second group of occurrences below depth 2000 m:

1. MOZÓW - depth 2176-2537m in 4 wells

2. WILCZE - depth 2431,9 1 well

3. PAPROĆ - depth 2609m 1 well

4. KALEJE - depth 3136m 1 well

5. ŻERKÓW - depth 3548,5m 1 well


(A1.2.5) 16 / 30

6. FLORENTYNA - depth 3865, 5m 1 well

The size of the body: Width - E.g. ŚCINAWA WEST 2-3 km; Length - E.g. ŚCINAWA WEST 4-10 km;

Height - First group of occurrences up to the depth 2000 m:

KULÓW - av. 1,41 m with av. 2,98% Cu and 96 ppm Ag,

LUBOSZYCE - av. 1,66 m with av.1,76% Cu and 57 ppm Ag,

SCINAWA WEST - av. 3,4 m with av. 1,47 % Cu and 54 ppm Ag,

ŚCINAWA NE - av. 2,0 m with av. 0,93%Cu and 88 ppm Ag,

BORZECIN - av. 0,51 m with av. 4,91% Cu,

MIRKÓW - av. 1,17 m with 1,56% Cu,

ŚLUBÓW - av. 0,2 m with av. 10,73% Cu and 164 ppm Ag,

ŻARKÓW - av. 1,13 m with av. 3,07 % Cu,

CZEKLIN - av. 0,23 m with av. 10,54% Cu

HENRYKOWICE - av. 1,18 m with av. 2,14% Cu and 19 ppm Ag,

JANOWO - av. 0,9 m with av. 2,28% Cu,

MILICZ - av. 1,86 m with av. 0,98% Cu,

SULMIERZYCE - av.1,60 m with av. 3,52% Cu

WARTOWICE WEST - 1,9-4,3 m with 0,88-1,5% Cu and 20-160ppm Ag

Second group of occurrences below depth 2000 m:

1. MOZÓW - 0,6-5,25 m with 2,6-4,8% Cu and 11-116 ppm Ag,

2. WILCZE - 0,55 m with 7,75% Cu and 417 ppm Ag,

3. PAPROĆ - 0,1 m with 21,48% Cu and 421 ppm Ag,

4. KALEJE - 1,0 m with 7,07% Cu,

5. ŻERKÓW - 2,8 m with 1,38% Cu and 22 ppm Ag,

6. FLORENTYNA - 1,0 m with 2,99% Cu and 33 ppm Ag.

*Remark: More than 500 wells in all Poland, where Zechstein Kupferschiefer ore series occurring, e.g.

from the Foresudetic Monocline and western border of Poland to SE part of Wielkopolskie

voivodeship, but also Łeba Uplift in Pomorskie voivodeship (N Poland).

Geological data:

Geological data are recorded from middle 1950-ties to present time as a result of huge prospecting

program for Cu-Ag ores which have been realized by Polish Geological Survey-Polish Geological

Institute, KGHM Polish Copper SA, MiedziCopper Ltd., and oil&gas wells too.

a) Stratigraphy - Uppermost part of the Rotliegendes and bottom of the Zechstein

b) Lithology - Sandstones, black shale, dolomites and limestones

c) Structure - Beds and rarely lenses in the southern part of the Foresudetic Monocline

Geochemical data:

Since 1960-ties geochemical data from drillholes and underground works are collected by the KGHM

Polish Copper SA and it subsidiary KGHM Cuprum Ltd., also by Polish Geological Survey-Polish

Geological Institute.

a) Rock chemistry - Au, Pt-Pd, Se, Pb, Zn, Mo, V, Ni, Co

Geophysical data:


(A1.2.5) 17 / 30

Regional seismic, gravimetric and magnetic works drillhole as geophysical methods; Seismic profiles

and seismic or micro seismic works.

METAL ENRICHMENT 2:

The Cu-Mo-W ore of the porphyry and skarn type near Myszków in Upper Silesia.

Geological data:

Metal bearing formation in porphyry, granites and different metacontact rocks of Paleozoic and

Proterozoic age have been discovered by the drillhole on the depth 170–1300 m in the middle of

1970-ties. The main occurrence and ore body is Nowa Wieś Zarecka-Myszków-Mrzygłód. Perspective

area are: Mysłów – 11 km2, Żarki-Kotowice – 20 km2, Zawiercie – 1,2 km2, Pilica – 12 km2, and Dolina

Bękowska – 11 km2. These areas were established by the cut-off 0,02% Cu, 0,001% Mo and W, while

metal enrichment were identified in approximately dozen drillholes.

a) Stratigraphy - Mainly Paleozoic rocks, Proterozoic too

b) Lithology - Porphyry, granitoids, diabase, skarn

c) Structure - Ore body, anomalies-occurrences are located near contact zone of two huge

tectonic blocks - Małopolski and Górnośląski. Ores forms are stockwork, veinlets, and

impregnation.

Geochemical data:

Since 1960-ties geochemical data from drillholes and underground works are collected by the KGHM

Polish Copper SA and it subsidiary KGHM Cuprum Ltd., also by Polish Geological Survey-Polish

Geological Institute.

a) Rock chemistry - Cu, Mo, W, Au, Bi, Ag, Te

Geophysical data:

Mainly seismic, gravimetry, magnetic profiles, drillholes geophysics

METAL ENRICHMENT 3:

Uranium, Peribaltic Syneclize, between Piaski on the Wiślana Spit to the north (Baltic Coast) and

Frombork and Pasłęk on a land near Baltic Coast to the south east. The approximate depth in meters

where the metal bearing formation was reached is about 800 m at Wislana Spit (Ptaszkowo, Krynica

Morska), but near Frombork and Pasłęk the depth is 1000–1200 m. Size of the body is: Width - At

Wiślana Spit 10 km, up to 75 km between Frombork – Pasłęk; Length - up to75 km between Pasłęk-

Malbork; Height - Av. 3.4 m with av. 0.34% U. The 23 wells out, of them 13 are located on Wiślana Spit

and 10 wells on the land, identified the given metal enrichment.

Geological data:

Data from investigation works carried on in the late 1970-ties - geophysics and wells. The main

sources of these information are:

Perspective resources of raw material in Poland at the end of 2009, Chapter: Uranium, Editors

S. Wołkowicz, T. Smakowski and S, Speczik (only in Polish version), PGI 2011 Warsaw

Miecznik J.B., Strzelecki R., Wołkowicz S., 2011 – Uranium in Poland – history of the

prospecting and prospects to discovery (only in Polish version). Przegląd Geologiczny

(Geological Review), vol. 59, no. 10., pp. 688-697.

1. Stratigraphy - Buntersandstone (lower or early Triassic)


(A1.2.5) 18 / 30

2. Lithology - Sandstone, conglomerate

3. Structure - Beds

Geochemical data:

a) Rock chemistry - V, Mo, Pb, Se

METAL ENRICHMENT 4:

Uranium, Rajsk (Bielsk Podlaski county, Podlaskie Voivodeship, NE Poland) where metal bearing

formation was reached from 400 m in the NE part up to 1200 m in the S and W part. The estimated

size of the body where metal enrichment has been identified is ca. 16 km2, av. 250 ppm U. The 62

wells, out of them 30 wells at Rajsk area identified the given metal enrichment.

Geological data:

a) Stratigraphy - Lower Ordovician

b) Lithology - Dictyonema shale

c) Structure - Bed

Geochemical data:

a) Rock chemistry - V 1100–2000 g/t, Mo up to 500 g/t

METAL ENRICHMENT 5:

The Fe-Ti with V ores at mafic and ultramafic rocks massif, Krzemianka and Udryń deposits, Suwalki

area, NE Poland at depth of 850–2700 m. The estimated size of this body is ca. 1340 million t of ore,

av. content 28% Fe, 7% TiO2 and 0.3% V2O5. The mineral enrichment has been identified in over 100

drillholes.

Geological data

The Suwalki Massif has been recognized during 1970-ties. Due to lack of effective technologies of

beneficiations of titanomagnetite ore and environmental problems on the surface, investigation

program was stopped in 1980-ties.

a) Stratigraphy – Proterozoic

b) Lithology - anorthosite, norite

c) Structure - stockwerk, lenses and beds

Geochemical data:

a) Rock chemistry - Ni, Co, Cu, Au

3.3.6 SERBIA

Two metal enrichments were identified below the depths where the temperature exceeds 100°C.

METAL ENRICHMENT 1:

Borska reka - Bor, Metals: Cu, Au. Coordinates: X= 4883100 – 4884300 Y= 7587300 – 7588200 Z = 346

m – 465 m. The depth in meters where the metal bearing formation was reached: (-10 m) – (-1005 m).

The extent of metal enrichment in not known. Size of the body: Width - maximum: 650 m (level -455

m), NE-SW; Length - maximum: 1450 m (level -455 m), NW-S; Height - open; >1000 m; the length of

mineralization, along the dip, has not been completely defined. The 63 drillholes including 21 drillhole

deeper then 1000m identified the given metal enrichment.


(A1.2.5) 19 / 30

Geological data:

These rocks (i.e. the Timok andesites; I phase of volcanic activity) occur in the eastern parts of the

Timok Magmatic Complex (TMC), where overlie Cenomanian and Turonian sediments. Timok

andesites are covered by Senonian sediments (Oštrelj sediments and Bor clastites) and the Metovnica

epiclastite.

a) Stratigraphy - Copper mineralization (metal enrichment) is situated in hydrothermally altered

andesites (predominantly amphibole andesite and high potassium trachyandesites) and their

pyroclasts. According to high precision U/Pb, 40Ar/39Ar age (von Quadt et al., 2002; Clark &

Ullrich, 2004), the Timok andesites ranged from 89.0±0.6 to 84.26±0.67 Ma (Upper Turonian

to Upper Santonian).

b) Lithology - According to their lithological, volcanological and petrographic characteristics, the

andesites are distinguished into the following facies: lava flows (coherent and autoclastic),

shallow intrusions – lava domes, dykes and sills and various volcaniclastic rocks. Volcanic

activity was predominantly subterrestrial in an earlier volcanic phase and subarial to

submarine in later volcanic phase (Drovenik, 1959; Đorđević & Banješević, 1997; Banješević

M., 2006, 2010). Small intercalations of marbles and skarns and mineralized dykes of

quartzdiorite porphyries are present, too. Copper mineralization has been deposited in

intensive hydrothermally altered andesite and their pyroclastites (Jelenković et al., 2016).

Products of K-alteration prevails. In the ore mineralization zone dominant are: silicification,

pyritization, argillization and sulphatization.

c) Structure - Structural setting of the mineralized area is complex. Prevails longitudinal fault

structures of NW-SE directions (parallel to regional structure in the Timok magmatic complex),

transverse (NE-SW) structures and, less represented diagonal E-W faults. According to their

dimensions, one can differentiate regional and local structures and as related to ore

mineralization, structures are of pre-ore, intra-mineralization and post-ore type. The most

dominant fault structure is Bor fault. It represents lower boundary of mineralized area.

Volcanic structures are difficult to recognize today, since, due to multi-stage volcanic activity

and post-volcanic tectonic movements, they have been destroyed.

Geochemical data

Major element variations of all magmatic bodies within the Timok Magmatic Complex follow typical

differentiation trends that are generally consistent with phenocryst assemblages (Kolb M. et al., 2013).

Concentrations of MgO, Fe2O3 total, TiO2, and CaO decrease with increasing SiO2, whereas K2O and

Na2O concentrations increase or remain constant. Concentrations of Al2O3 and P2O5 first remain

constant with increasing SiO2, then decrease at SiO2 >55 wt%. K2O increases slightly with increasing

SiO2, up to 60 wt% SiO2.

a) Rock chemistry - Unaltered hornblende-biotite-pyroxene andesites as phenocrysts contain andesine

(40–52, mean 45% an), hornblende, subordinated biotite or augite, or both. Silica is mostly 54–60%,

Na2O > K2O, lime is in general equal to the sum of alkalies, the rocks correspond to calc-alkaline

magma (Karamata et al., 2002).

Geophysical data


(A1.2.5) 20 / 30

1. Gravity Map - Bouguer anomaly map 1 : 500 000, Sheet Belgrade Bilibajkić, P., Mladenović, M.,

Mujagić, S., Rimac, I, 1979., Explanation for the Gravity Map of SFR Yugoslavia – Bouguer Anomalies –

1 : 500 000, Federal Geological Institute, Belgrade.

2. Gravity Map - Bouguer anomaly map 1 : 25 000, Archive of RTB Bor.

3. Gravity Map - Bouguer anomaly map 1 : 5 000 Bilibajkić, P., Bilibajkić, D., 1982, Report on detail

gravity and geomagnetic survey at the site Borska Reka, Geophysical Institute, Belgrade. Surface

geomagnetic surveys

4. Geomagnetic Map – Magnetic field vertical (Z) component map 1 : 500 000, Sheet Belgrade

Stojković, M., Ćirić, B., Damnjanović, K., 1974, Explanation for the Geomagnetic Map of SFR Yugoslavia

– Anomalies of Vertical Intensity – 1 : 500 000, Geomagnetic Institute, Belgrade.

5. Geomagnetic Map – Magnetic field vertical (Z) component map 1 : 25 000, Archive of RTB Bor.

6. Geomagnetic Map – 1 : 5 000 Bilibajkić, P., Bilibajkić, D., 1982, Report on detail gravity and

geomagnetic survey at the locality Borska Reka, Geophysical Institute, Belgrade.

*Remark: Extra surface or airborne geophysical surveys which provide additional data related to the

metal enrichment has been reported:

Aeromagnetic Map - 1 : 200 000 and 1 : 100 000

Vukašinović, S, 1994, Explanation for the Aeromagnetic Maps of the Republic of Serbia 1 : 100

000, Geoinstitut, Belgrade.

Vukašinović, S, 1995, Explanation for the Aeromagnetic Maps of the Republic of Serbia 1 : 200

000, Geoinstitut, Belgrade.

Vukašinović, S, 2005, Anomalous magnetic field and geological setting of the Republic of

Serbia, Geoinstitut, Belgrade.

Vukašinović, S, 2015, Review and interpretation of the Aeromagnetic Map of the Republic of

Serbia 1 : 100 000 (explanation for the map).

Airborne magnetic survey – Timok Project, 2006, Archive of Avala Resources Ltd. (previously

Dundee Precious Metals Inc).

METAL ENRICHMENT 2:

Čukari Peki - Bor; Metals: Cu, Au, Locality: Serbia, Brestovac Coordinates: X= 4875000 – 4877000 Y=

7590000 – 7593000 Z = 300 m – 400 m, approximately 375 m amsl. 44° 01’ 30” N and longitude 22°

08’ 00” E. Mineralization occurs at depths between 400 m below surface to greater than 2000 m (0 m

– > -1500 m). The extent of the metal enrichment is not known, but estimated: Width ca. 1000 m, N-S;

Length - ca. 1500 m, W-S; Height – open >1500 m; the length of mineralization, along the dip, has not

been completely defined. The top of the LZ mineralization occurs at depths below surface ranging

from approximately 1400 meters in the west to 750 meters in the east. More than 50 drillholes

identified the given metal enrichment.

Geological data

In summary, the geology of the Brestovac-Metovnica mineralized area includes first phase andesites,

volcaniclastics and sediments typical of the eastern block, a small area of second-phase pyroxene-

bearing basaltic andesite typical of the western block, and unconformably overlying Miocene

sediments in the centre of the area of exploration (http://www.reservoirminerals.com/).

http://www.reservoirminerals.com/


(A1.2.5) 21 / 30

a) Stratigraphy - Metal enrichment is situated in hydrothermaly altered andesites of I phase

(predominantly amphibole andesite and high potassium trachyandesites) and their pyroclasts.

This rocks (i.e. the Timok andesites, or I volcanic phase) occur in the eastern parts of the

Timok Magmatic Complex (TMC), where overlie Cenomanian and Turonian sediments. Timok

andesites are covered by Senonian sediments (Oštrelj sediments and Bor clastites) and the

Metovnica epiclastite. According to high precision U/Pb, 40Ar/39Ar age (von Quadt et al.,

2002; Clark & Ullrich, 2004), the Timok andesites ranged from 89.0±0.6 to 84.26±0.67 Ma

(Upper Turonian to Upper Santonian).

b) Lithology - According to their lithological, volcanological and petrographic characteristics, the

andesites are distinguished into the following facies: lava flows (coherent and autoclastic),

shallow intrusions – lava domes, dykes and sills and various volcaniclastic rocks. Volcanic

activity was predominantly sub terrestrial in an earlier volcanic phase and subarial to

submarine in later volcanic phase (Banješević M., 2006, 2010). Small intercalations of marbles

and skarns and mineralized dykes of quartzdiorite porphyries are present, too. The host rocks

to all the mineralization styles consist of various hornblende and hornblende-biotite andesites,

andesite breccias, hydrothermal breccia, and relatively rare diorite porphyry.

c) Structure - A regionally significant NNW-striking fault cutting through the Brestovac river

valley is probably the largest fault in the mineralized area. This fault marks the boundary,

between the first phase andesitic volcanism in the eastern block and the second phase

volcanism in the western block and could represent a major basement suture. There is also at

least one subordinate fault trend which varies in strike from E-W to NE-SW. These faults also

have both apparent sinistral and dextral slip senses.

Geochemical data

Unaltered hornblende-biotite-pyroxene andesites as phenocrysts contain andesine (40-52, mean 45%

an), hornblende, subordinated biotite or augite, or both. Silica is mostly 54-60%, Na2O > K2O, lime is

in general equal to the sum of alkalis, the rocks correspond to calc-alkaline magma (Karamata et al.,

2002).

a) Rock chemistry: Major element variations of all magmatic bodies within the Timok Magmatic

Complex follow typical differentiation trends that are generally consistent with phenocryst

assemblages (Kolb M. et al., 2013). Concentrations of MgO, Fe2O3 total, TiO2, and CaO decrease with

increasing SiO2, whereas K2O and Na2O concentrations increase or remain constant. Concentrations of

Al2O3 and P2O5 first remain constant with increasing SiO2, then decrease at SiO2 >55 wt%. K2O

increases slightly with increasing SiO2, up to 60 wt% SiO2. Incompatible element concentrations (e.g.,

Th, La) generally do not correlate with SiO2 in the TMC. Enrichment in light REE (LREE) and relatively

flat heavy REE (HREE) patterns are general features of the dataset for the TMC. Large ion lithophile

elements (LILE) such as U, Th, and Pb are enriched.

Geophysical data - Induced polarization, DC resistivity, SP and other geoelectrical surveys

3.3.7 SLOVAK REPUBLIC

Two metal enrichment were identified below the depths where the temperature exceeds 100°C in

Slovak Republic.


(A1.2.5) 22 / 30

METAL ENRICHMENT 1:

Geographical data - As enrichment in geothermal waters in the Durkov geothermal structure in

eastern Slovakia. The structure lies in between the Slanské Mountains and the Slovenske Rudohorie

Mountains (Franko et al. 1995; Vranovská et al., 2015).

The depth in meters where the metal bearing formation was reached:

(1) GTD-1: Q = 56 l.s-1, Tbtm = 144˚C, Twh = 125˚C, TDS = 30 000 mg.l-1 , h = 3210 m.b.t.;

(2) GTD-2: Q = 50 l.s-1, Tbtm = 154˚C, Twh = 129˚C, TDS = 31 000 mg.l-1 , h = 3151 m.b.t.;

(3) GTD-3: Q = 65 l.s-1, Tbtm = 131˚C, Twh = 123˚C, TDS = 31 000 mg.l-1 , h = 2252 m.b.t.

Estimated size of this body - 33.6 km2 where the formation reaches 2000 m of thickness

Detailed dimensions of the deep geothermal reservoir in the Durkov area are accessible true reports

which are available in a manuscript form and are in Slovak language, and can be accessed through the

website of Digital archive of the State geological institute of Dionýz Štúr, or personally at our address

in Bratislava (see Slovak references in the reference list). Here given is only an estimate where the

Durkov structure aquifer dolomites are as thick as 2000 m. Note that the depth and thickness

increases towards the east. More information of the dimension of the whole structure (and not only

the 2000 m area) might be found in Vranovská et al., 2015 & Hók et al. 2001. The geothermal reservoir

is located in Mesozoic carbonates (Middle and Upper Triassic) and also in basal clastics of the

Carpathian.

Geological data:

a) Stratigraphy -Middle and Upper Triassic dolomites (up to 2000 m thick) covered by Neogene

sediments, andesites and vulcanoclastics.

b) Lithology - Secondary As-enrichment in a Triassic sedimentary dolomite deposit in the

reservoir brine. (Vranovská et al., 2015).

c) Structure - The geothermal structure is a part of the Kosice Basin in Eastern Slovakia

(Vranovská et al., 2015). The Kosice Basin is delimited by the volcanic Slaánské Mountains,

which have a strong impact on the genesis of geothermal waters and are the principal source

of trace elements.

Geochemical data:

Infiltration of meteoric water and dissolution of evaporates, especially halite, in the overlying Neogene

formation (b) reaction of the highly mineralized water with Hg–As–Sb type of mineralization, related

to the Neogene volcanism, and, (c) accumulation of As-rich geothermal water in Triassic carbonates

with an additional input of CO2 (Vranovská et al., 2015).

a) Rock chemistry - dolomite

b) Fluid chemistry - Na-Cl type of geothermal water, trace elements: As, Fe, Mn, Cd, Cr, Cu, Li, Pb, Sr,

Zn, F, I, Br. Only As has high concentrations in the Durkov structure. (Table 1, Vranovská et al., 2015).

Geophysical data:

All data of the cores is publicly accessible in manuscripts archived at the State Geological Institute of

Dionýz Štúr in Bratislava (webpage: www.geology.sk). Data are accessible online after registration, or

hand-printed personally in the archive.

*Remark - GeoMaps of subsurface geothermal reservoirs are available in “Geothermal and mineral

water sources” (Fendek et al., 2002)


(A1.2.5) 23 / 30

METAL ENRICHMENT 2:

Note that this metal bearing zone is drilled but not at temperatures of > 100°C. At the bottom of the

complex however, temperatures are expected to be close to 100°C in some zone's. Situated in the

Eastern Carpathian metalogenetic region. One drillhole identified the metal enrichment.

Geological data:

a) Stratigraphy - Neogene Volcanoclastic and andesitic deposits

b) Lithology- andesitic, volcanoclastic

Geochemical data - Epigenetic mineralization is characterized by Fe, Cu, Mo, Bi, Pb, Zn, Au, Ag, Te, Sb,

Hg, and As (Vranovska, 2015)

a) Rock chemistry - Cu–Pb–Zn–Mo association are most common (Mello et al. 2005)

4 Conclusions

Data collected from the 23 European countries revealed the potential of some countries for

CHPM2030 EGS application providing the European overview on data availability. The 19 countries out

of 23 which participated in this survey reported that drillholes with temperatures exceeding 100°C

exists in their country (Table 1). The number of such drillholes varies from 1 (Ireland) to 2809

(Germany).

Among them, eight countries mentioned the identification of metal enrichment (Austria, Belgium,

Cyprus, Hungary, Poland, Serbia, Slovak Republic and UK, while five of those (Belgium, Hungary,

Poland, Serbia and Slovak Republic) provided more detailed insight into these metal enrichments

providing some data on geographical, geological, geochemical and geophysical data (see text for more

information). These countries could be of further interest of the CHPM2030 interest. Since the data of

the project’s interest only partly publicly available or not available at all, further cooperation with

National experts and possible contact to Organizations in charge/owning the data will be necessary to

obtain all relevant information.

5 References

5.1.1 BELGIUM

K. Piessens (2001) Metallogenese van de gemineraliseerde schuifzone te Sint-Pieters-Kapelle

(Brabant massief, België). PhD manuscript (KULeuven)

K. Piessens,, P. Muchez, W. Viaene, A. Boyce, W. De Vos, M. Sintubin, T. Debackere (2000). Alteration

and fluid characteristics of a mineralised shear zone in the Lower Palaeozoic of the Anglo-Brabant

belt, Belgium. Journal of Geochemical Exploration 69–70 (2000) 317–32

Petitclerc E. and Vanbrabant Y (2011). Développement de la plate-forme Géothermique de la

Wallonie, Final Report. (2011). Direction Générale Opérationnelle de l’Aménagement du Territoire,

du Logement, du Patrimoine et de l’Energie (DGO4), Département de l’Energie. 228 P.


(A1.2.5) 24 / 30

5.1.2 CYPRUS

The mineral map of Cyprus (2007)

(http://www.moa.gov.cy/moa/gsd/gsd.nsf/All/95039382098491A6C225744E002172B8/$file/Miner

alGR.jpg?OpenElement)

Bulletin 1 (1963): The Mineral Resources and Mining Industry of Cyprus by L.M. Bear (EN)

Bulletin 3 (1969): An Airborne Magnetic and Electromagnetic Survey in Cyprus by Hunting Geology

and Geophysics Ltd (EN)

5.1.3 GREECE

Fytikas, M. and Kolios, N. (1992): Geothermal exploration in the west of the Nestos delta. Acta

Vulcanologica, Marinelli Volume, 2, 237-246

Fytikas, M. (2014): Geothermy in Greece Resources, Applications, Perspectives. Series Papers

Bioclimatic Design "Geothermy, the great RES missing in Greece" (Athens, January 17-24, 2014)

Kamakaris, V. (2010): Geothermal Research in Milos Island – A review of geothermal Data. National

Technical University of Athens, Honors Thesis, 180 p.

Vrellis, G., Arvanitis, A., and Mpimpou - Mpakoula, A. (2009): Geothermal Drillings: Planning,

Construction and Overcoming Problems. International Forum "Geothermal energy on Stage"

(Thessaloniki, December 11-12, 2009)

5.1.4 HUNGARY

Csaba BAKSA et al, 1984: Összefoglaló jelentés a külszíni mélyfúrási kutatásokról, Vol I-VI -

Manuscript, National Archive of Mining, Geology and Geophysics, 12588, Budapest

Scharek P. (szerk.) 2004: Földtani formációk elemtartalom adatbázisa 2. – Kézirat, Országos

Bányászati Földtani és Geofizikai Adattár – T 21163

5.1.5 LUXEMBOURG

Schintgen T. (2015) Exploration for deep geothermal reservoirs in Luxembourg and the surroundings

– perspectives of geothermal energy use. Geothermal Energy (2015) 3:9 DOI 10.1186/s40517-015-0028-2

5.1.6 POLAND

Perspective resources of raw material in Poland at the end of 2009, Chapter: Copper ores, Editors S.

Wołkowicz, T. Smakowski and S, Speczik (only in Polish version), PGI Warsaw, 2011

Oszczepalski S., Chmielewski A. 2015 - Predicted metallic resources in Poland presented on the

prospective maps at scale 1 : 200 000 - copper, silver, gold platinum palladium in the

Kupferschiefer ore series. Przegląd Geologiczny (Geological Review), vol. 63 (9), pp. 534-545 (in

Polish with English summary) Oszczepalski S., Speczik S., Małecka K., Chmielewski A., 2016 –

Prospective copper resources in Poland. Gospodarka Surowcami Mineralnymi - Mineral Resources

Management, 31 (2) (in print).

Oszczepalski S., Speczik S., Małecka K., Chmielewski A., 2016 – Prospective copper resources in

Poland. Gospodarka Surowcami Mineralnymi - Mineral Resources Management, 31 (2) (in print).

Miecznik J.B., Strzelecki R., Wołkowicz S., 2011 – Uranium in Poland – history of the prospecting and

prospects to discovery (only in Polish version). Przegląd Geologiczny (Geological Review), vol. 59,

no. 10., pp. 688-697.


(A1.2.5) 25 / 30

Nieć M., 2003 - Geo-economic evaluation of vanadiferous titanomagnetite deposits in Suwałki massif

in Poland. Gospodarka Surowcami Mineralnymi - Mineral Resources Management, 19 (2).

5.1.7 PORTUGAL


5.1.8 SERBIA

von Quadt, A., Peytcheva, I., Cvetković, V., Banješević, M. & Koželj, D. 2002: Geochronology,

geochemistry and isotope tracing of the Cretaceous magmatism of East Serbia as part of the

Apuseni–Timok–Srednogorie metallogenic belt. 17th Congress of Carpathian– Balkan Geological

Association, Geologica Carpathica, Special issue, 175–177.

Clark, H.A. & Ullrich, D.T. (2004): 40Ar/39Ar age data for andesitic magmatism and hydrothermal

activity in the Timok Massif, eastern Serbia: implications for metallogenetic relationships in the Bor

copper-gold subprovince. Mineralium Deposita, 39: 256–262.

Banješević M., 2006: Gornjokredni magmatizam Timočkog magmatskog kompleksa [Upper

Cretaceous magmatism of the Timok magmatic complex – in Serbian, with an English abstract]. PhD

thesis, Faculty of Mining and Geology, Belgrade University, Belgrade, 184 p.

Banješević M., 2010: Upper Cretaceous magmatic suites of the Timok Magmatic Complex. Annales

Géologiques de la Péninsule Balkanique. Belgrade, 71, 13–22.

Đorđević, M. & Banješević, M., 1997: Geologija južnog dela Timočkog magmatskog kompleksa, Tumač

geološke karte 1:50000 [Geology of the southern part of the Timok Magmatic Complex, Booklet

and Geological Map 1:50000 – in Serbian]. Federal Ministry of Economy FR Yugoslavia, Belgrade,

171 p.

Drovenik, M., 1959: Complement to understanding the Timok eruptive massive rocks. Rasprave in

poročila, Geologija, 5: 11–21 (in Slovenian).

Janković S., Jelenković R., Koželj D., 2002: The Bor Copper and Gold Deposit. Mining & Smelting Basin

Bor (RTB Bor) – Copper Institute Bor (CIB). Querty-Bor, Bor, 298.

Jelenković, R., Milovanović, D., Koželj, D., Banješević, M., 2016: The Mineral Resources of the Bor

Metallogenic Zone: A Review. Geologia Croatica, Vol. 69/1. 143-155. doi: 10.4154/gc.2016.11

Karamata S., Knežević-Đorđević V., Milovanović D., 2002: A Review of the evolution of Upper

Cretaceous Paleogene magmatism in the Timok Magmatic complex and the associated

mineralization. Geology and metallogeny of copper and gold deposits in the Bor metallogenic zone.

RTB Bor company and Copper Institute Bor, Querty-Bor, 15-29.

Kolb, M., von Quadt A., Peytcheva, I., Heinrich, C. A., Fowler, S. J. and Cvetković V., 2013: Adakite-like

and Normal Arc Magmas: Distinct Fractionation Paths in the East Serbian Segment of the Balkan-

Carpathian Arc, fluid chemistry, trace elements. Journal of Petrology, Volume 54, Number 3, 421-

451 2013 doi:10.1093/petrology/egs072

http://www.reservoirminerals.com/ NI43-101 PRELIMINARY ECONOMIC ASSESSMENT OF THE

CUKARU PEKI UPPER ZONE DEPOSIT, SERBIA, MARCH 2016

5.1.9 SLOVAK REPUBLIK

Vranocská A.; Bodis D.: Sracek O. & Zenisova Z. (2015). Anomalous arsenic concentrations in the

Durkov carbonate geothermal structure, eastern Slovakia. Environ Earth Sci (2015). 73:7103–7114).



(A1.2.5) 26 / 30

Mello J.; Ivanicka J.; Bezak V.; Biely A.; Elecko M.; Grecula P.; Gazdacko L.; Jacko S.; Janocko J. &

Kobulsky J. (2005). Explanations to the geological map 1:200,000, sheet 37, (in Slovak). Kosice,

Bratislava, Ministry of Environment

Hok J.; Kahan S. & Aubrecht R. (2001). Geology of Slovakia (in Slovak). Comenius University Editorial,

Bratislava

Fendek, M.; Porazikova, K.; Stefanovicova, D. & Supukova, M. (2002). Geothermal and mineral water

sources, Map 1:500 000. In: Landscape Atlas of the Slovak Republic. 1st edition. Bratislava –

Ministry of Environment of the Slovak Republic, Banska Bystrica – Slovak Environmental Agency

(2002), 214-215.

MANUSCRIT data of cores and wells and geothermal research (in Slovak language): (1) Vranovská

Andrea; Bondarenková Zora; Král Miroslav and Drozd Vladimir. (1999). Košická kotlina - štruktúra

Ďurkov - hydrogeotermálne zhodnotenie, vyhľadávací prieskum Bratislava: SLOVGEOTERM, Archív

Geofond (ID 83225), 90 str. (2) Vranovská Andrea. (2001). Ďurkov - hydrogeologické a

technologické poznatky z dlhodobej skúšky GTD-1, GTD-2 a GTD-3, podrobný HGP Bratislava:

SLOVGEOTERM, Archív Geofond (ID 84439), 19 pp.

5.1.10 SLOVENIA

Convenio con la empresa nacional Adaro de investigaciones mineras SA para el desarrollo de trabajos

de investigación geotérmica dentro del programa 234. Otras fuentes de energía. 1984. IGME

(http://info.igme.es/SidPDF%5C019000%5C560%5CEstudio%20legal%20y%20administrativo%20de

l%20aprovechamiento%20de%20los%20recursos%20geotermicos%5C19560_0002.pdf) Estudio de

las posibilidades de explotación de energía geotérmica en almacenes profundos de baja y media

entalpia del territorio nacional. IGME. 1981

http://www.igme.es/Geotermia/Ficheros%20PDF/3%20Bajamedia%20entalp%EDa.pdf Inventario

general de manifestaciones geotérmicas en el territorio nacional (1976).

http://www.igme.es/Geotermia/IGMEinventario.htm Estimación de los recursos y reservas

geotérmicos de España.

http://www.idae.es/uploads/documentos/documentos_11227_e9_geotermia_A_db72b0ac.pdf

Documentos sobre la Geologia del Subsuelo de España. J.L. Martínez Abad y R. Querol Muller.

http://info.igme.es/geologiasubsuelo/GeologiaSubsuelo/Documents.aspx Contribución de la

exploración petrolífera al conocimiento de la geología de España. J. Mª Lanaja.

http://info.igme.es/sidPDF/065000/081/Informes/65081_0001.pdf Columnas de Sondeos de la

Cuenca Vasco Cantábrica. CIEPSA 1966

http://info.igme.es/geologiasubsuelo/docs/CIEPSA_1966_Columnas_Sondeos_Cuenca_Vasco_Cant

abrica.pdf

http://akvamarin.geo-zs.si/t-jam_boreholes/ and

http://www.arcgis.com/home/webmap/viewer.html?webmap=f82fe0f737174219a354f4209ea744

8a&extent=12.1518,45.3238,20.2487,49.1158.

5.1.11 UK

Andrews, J.N., Hussain, N., Ford, D.J. and Youngman, M.J. (1989). Geochemistry in relation to Hot Dry

Rock development in Cornwall, Volume 3. The use of natural radioelement and radiogenic noble

gas dissolution for modelling the surface area and fracture width of a Hot Dry Rock system. British

Geological Survey research report, SD/89/2. Volume 3, 109pp.


(A1.2.5) 27 / 30

Bromley, A.V. & Thomas. L.J. (1988). Structural controls on the circulation of thermal brines at South

Crofty Mine, Cornwall. In: Louwrier, K. and Garnish, J.K., (eds.) 1988.

Bromley, A. (1989). Water - rock interaction in southwest England: The evolution of the Cornubian

orefield. Field guide from the Sixth International Symposium on Water-Rock Interaction (WRI-6),

Malvern, UK, 3-13 August 1989, 111pp.

Bromley, A.V., Thomas, L.J., Shepherd, T.J. and Darbyshire, D.P.F. (1989). Geochemistry in relation to

Hot Dry Rock development in Cornwall, Volume 5. Mineralogy and geochemistry of the

Carnmenellis granite. British Geological Survey research report, SD/89/2. Volume 5, 109pp.

Edmunds, W.M., Andrews, J.N., Bromley, A.V., Richards, H.G., Savage, D. and Smedley, P.L. (1989).

Geochemistry in relation to Hot Dry Rock development in Cornwall, Volume 1. Applications of

geochemistry to Hot Dry Rock geothermal development: an overview. British Geological Survey

research report, SD/89/2. Volume 1, 109pp.

Richards, H.G., Wilkins, C., Kay, R.L.F. and Savage, D. (1989). Geochemistry in relation to Hot Dry Rock

development in Cornwall, Volume 2. Geochemical results from the Rosemanowes Hot Dry Rock

system 1986-88. British Geological Survey research report, SD/89/2. Volume 2, 240pp.

Richards, H.G., Savage, D. and Shepherd, T.J. (1989). Geochemistry in relation to Hot Dry Rock

development in Cornwall, Volume 7. Geochemical prognosis for a commercial-depth Hot Dry Rock

system in south-west England. British Geological Survey research report, SD/89/2. Volume 6, 80pp.

Richards, H.G., Willis-Richards, J., Pye J. (1991). A review of geological investigations associated with

the UK Hot Dry Rock programme. Annual Conference of the Ussher Society, January 1991

Savage, D., Bateman, K., Milodowski, A., Cave, M.R., Hughes, C.R., Green, K., Reeder, S. and Pearce, J.

(1989). Geochemistry in relation to Hot Dry Rock development in Cornwall, Volume 6. Experimental

investigation of granite-water interaction. British Geological Survey research report, SD/89/2.

Volume 6, 162pp.

Smedley, P.L., Bromley, A.V., Shepherd, T.J. and Edmunds, W.M. (1989). Geochemistry in relation to

Hot Dry Rock development in Cornwall, Volume 4. Fluid circulation in the Carnmenellis granite:

hydrogeological, hydrogeochemical and palaeofluid evidence. British Geological Survey research

report, SD/89/2. Volume 4, 117pp.

Tellus-project. (2013). GEOCHEM survey programme, magnetic and radiometric data,

http://www.tellusgb.ac.uk/Geophysics.html. Data managed by British Geological Survey.

Thomas, L.J. and Milodowski, A.E. (1988). Alteration mineralogy. In: Edmunds, W.M. et al. 1988, 57-

80.


(A1.2.5) 28 / 30

6 Appendix 1. LTPs contact list:

Country Expert Email Organization

Austria Gregor Götzl

Edith

Haslinger

[email protected]

[email protected]

Geologische Bundesanstalt für

Österreich

Austrian Institute of

Technology

Belgium Yves

Vanbrabant

Rindert

Janssens

Estelle

Petitclerc

Kris Piessens

[email protected]

[email protected]

[email protected]

[email protected]

Geological Survey of Belgium




Czech

Republic

Croatia Lilit Cota

Staša Borović

[email protected]

[email protected]

INA Industrija nafte d.d.

Croatian Geological Survey

Cyprus Christodoulos

Hadjigeorgiou

Costas

Constatinou

[email protected]

[email protected]

Geological Survey Department

Geological Survey Department

Finland Markku Iljina [email protected] YKL

Germany Benno Kolbe [email protected] BDG

Greece Koukouzas

Nikolaos

[email protected] Association of Greek

Geologists (A.G.G.)

Hungary Péter Scharek [email protected] Hungarian Geological Society

Ireland Ric Pasquali [email protected] Geothermal Association of

Ireland

Italy

Luxembourg Robert

Colbach

[email protected] Service Géologique du

Luxembourg

Netherlands Hein Raat [email protected]

[email protected]

TNO - Geological Survey of the

Netherlands

Poland Krzysztof

Galos

[email protected] Polish Association of Mineral

Asset Valuators

https://www.researchgate.net/institution/GBA-Geologische_Bundesanstalt_fuer_Oesterreich

https://www.researchgate.net/institution/GBA-Geologische_Bundesanstalt_fuer_Oesterreich

mailto:[email protected]


(A1.2.5) 29 / 30

Country Expert Email Organization

Portugal Mónica Sousa [email protected] Portuguese Association of

Geologists

Slovak

republic

Branislav

Fričovský

branislav.fricovsky[a]geology.sk State geological institute of

Dionýz Štúr

Slovenia Andrej

Lapanje

[email protected] Geological Survey of Slovenia

Spain Manuel

Regueiro

[email protected] Ilustre Colegio Oficial de

Geólogos de España (Spanish

Official Professional

Association of Geologists)

Serbia Zoran

Stevanovic

[email protected] Serbian Geological Society

Sweden Gerhard

Schwarz

[email protected] Geological Survey of Sweden

Switzerland Jean-Bernard

Joye

[email protected] CHGeol

Ukraine

UK Christopher

Rochelle

[email protected] British Geological Survey

7 Appendix 2. Template for data collection by the EFG Linked third Parties in the frame of Task 1.2.5 - European data integration and evaluation CHPM2030, Work-package 1 - Methodology framework definition

7.1 Background

The objective of CHPM2030 WP1 is to prepare the conceptual framework for a novel EGS for the

production of energy and the extraction of metals from ore deposits located at great depths. First we

need to synthesise our knowledge on deep metal enrichments that could be converted into an

“orebody EGS”, and to investigate the characteristics of these bodies. We aim to discover and examine

the geological, tectonic, geochemical, and petrologic factors that define the boundary conditions of

such novel EGS both in terms of energy and potential for metal recovery.

The information will be obtained by reviewing past investigations in Europe that have resulted in

public access geological and geothermal datasets. In addition to these data, associated publications

and studies will also be reviewed. EFG Linked Third Parties will collect publicly available data at

national level on deep drilling programmes, geophysical and geochemical explorations and any kind of

geo-scientific data related to the potential deep metal enrichments. They will also collect data on the

national geothermal potential. The task provides a “European outlook” on data availability in order to

identify data gaps. A horizontal task is to connect two insofar unconnected communities: mining and

geothermal earth science professionals for a common goal on EU and national levels.


(A1.2.5) 30 / 30

In the third year of the project implementation, within WP6 - Roadmapping and Preparation for Pilots,

the EFG Linked Third Parties will assess the geological data on suitable ore-bearing formations and

geothermal projects, which were collected in WP1, in relation with the potential application of the

CHPM technology.

In this template we use the term “metal enrichment”. For this term, please consider the geological

formations in which the metal content is at least five times higher than the average in the given

formation type. This term also includes the “real ore bodies” which have economic value on their own.

Please consider the following metals: Cu, Zn, Pb, Fe, As, Sb, Ag, Au, Co, Cr, Ni, U, Sn, W, Mo

On the last page of the data collection template please provide a list of references which were used

for filling the form. For the references in your national language, please provide an English translation.

7.2 Data on drilling programmes

As we want to apply an EGS system, in the data collection we are looking for the depths where the

temperature is above 100°C. Please take the average geothermal gradient in your country and during

the data collection consider only drillholes which reached at least this depth. It can be different in the

different areas of Europe, depending on the geothermal characteristics.

1. Are there any drillholes in your country which reached the depths where the temperature

exceeds 100°C?

2. If yes, please indicate the number of these drillholes:

3. Are the data from these drillholes publicly available:

a. yes, for each drillhole

b. yes, for a part of them

c. no publicly available data

4. If yes, please indicate the number of drillholes where there are publicly available data:

5. Is there any metal enrichment in your country identified below the depths where the

temperature exceeds 100°C?

a. yes

b. no

6. If yes, please indicate the number of the identified metal enrichments:

7.3 Data on deep metal enrichments

Below you can take multiplied questions, (Metal enrichment 1, 2, 3...) according to the number of

identified metal enrichments. Please answer the questions separately for each metal enrichment

which has been identified in your country.

Metal enrichment 1:

1. Geographical data of metal enrichment (locality, coordinates) :

2. Please indicate the depth in meters where the metal bearing formation was reached:

3. Is the extent of the metal enrichment known?

a. yes

b. no

4. If yes, please indicate the estimated size of this body:

a. width:

b. length:

c. height:


(A1.2.5) 31 / 30

5. How many drillholes identified the given metal enrichment:

6. Geological data from the metal enrichment (please provide a few lines summary and the

most important publications/links which are relevant):

a. Stratigraphy

b. Lithology

c. Structure

7. Geochemical data (please provide a few lines summary and the most important

publications/links which are relevant):

a. rock chemistry, trace elements

b. fluid chemistry, trace elements

8. Geophysical data (please provide a few lines summary and the most important

publications/links which are relevant):

a. Normal resistivity logs

b. Fluid resistivity logs

c. Spontaneous-potential logs

d. Acoustic logs

e. Gamma logs

f. Other

9. Are there any surface or airborne geophysical surveys which provide additional data

related to the metal enrichment?

a. yes

b. no

10. If yes, please specify these geophysical methods:

Metal enrichment 2:

Metal enrichment 3:

7.4 Personal data

1. Your name:

2. Your organisation:

3. Your country:

Thank you for your cooperation!

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